Led light re-direction accessory

ABSTRACT

Apparatus and associated methods relate to development of a LED system with high thermal dissipation power relative to the system weight by the inclusion of open regions. The open regions reduce the weight of the optical system while improving airflow. Associated optics are described to efficiently and evenly distribute the light from an LED by tailoring the optical distribution. In addition, circuitry and methods are described to allow for the LED system to operate with existing power sources such as ballast or offline AC voltage sources or both.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.15/215,964 titled “LED Lighting,” filed by Frank Shum on Jul. 21, 2016,which is a Continuation-in-Part of U.S. patent application Ser. No.14/952,079 titled “LED Lighting,” filed by Frank Shum on Nov. 25, 2015,which claims the benefit of U.S. Provisional Application Ser. No.62/141,010 titled “LED Lighting,” filed by Frank Shum on Mar. 31, 2015.

This application incorporates the entire contents of the foregoingapplications herein by reference.

TECHNICAL FIELD

Various embodiments relate generally to improved LED (light emittingdiode) lighting sources, and some embodiments relate particularly tolightweight improved thermal management. Other embodiments relate tooptics with optional accessories with tailored distributions targetedfor particular optical distributions. Other Embodiments relate toelectronics necessary for operation of the LED system with legacyballast.

BACKGROUND

The field of LED lighting has made tremendous progress, however thermalmanagement remains a challenge, in particular where the high lightoutput is required relative to the allowable size of LED lightingsystem. This is a particular issue, namely, to replace high light outputand high light density lamps and fixture. One such area that remains achallenge is high intensity discharge (HID) Lamps that have very highlight output. For example, a 400 W HID lamp of less than 300 mm long and120 mm diameter will have more than 35,000 lumens.

Types of HID lamps include metal halide lamp, high pressure sodium lampand low pressure sodium lamps. These types of lamps require a warm upperiod of 1 to 15 minutes to reach 90% of their full light output. Aftera lamp has been operating for a period of time and then extinguished, itcannot be immediately turned back on. Before the lamp can be turned backon, the arc tube must have a chance to cool down or the lamp will notrestart. This period of time is called the restrike time. Restrike timesfor traditional probe-start MH lamps can take 15 minutes or longer whilerestrike times for pulse-start MH lamps are generally much shorter. Thelong warm up time and long restrike time are a disadvantage. HID lampsmay also contain mercury, a hazardous material, and may have onlymoderate life spans of about 10,000-20,000 hours, some may have rapidlumen depreciation in the first 3000-5000 hours.

In addition, HID lamps are an omni-directional light source which may bedifficult to efficiently redirect into a more useful and efficientdistribution. The optics used for redirecting the light can be expensiveand lossy. For example, a fixture light loss factor, or the optical lossmay typically be around 30%. So the moderate efficiency of a HID lamp isimmediately discounted by 30%. It is also typically difficult to controlthe light, resulting glare that is not only wasted but a source ofvisual discomfort.

SUMMARY

Apparatus and methods relate to a lighting system having a uniquecombination of one or more of the following sub systems including: alight emitting diode (LED), a heatsink, an electronic driver, a primaryoptic that redirects at least a portion of the raw LED lightdistribution into a primary optical distribution, a secondary opticalaccessory that redirects at least a portion of the primary opticaldistribution into a secondary optical distribution, and an electronicaccessory. The system may be an optical system such as, for example, alamp, a fixture, a luminaire, a module, an optical sub system or a lightengine. The sub systems, may be novel alone or in combination with othersub systems. The sub systems, or a combination thereof, may be novel andneed not be related to LEDs.

In various embodiments, a set of combined geometries may provide forimproved air flow to a heatsink, thus improving thermal dissipation. Insome embodiments, the heat sink construction may allow for reducedweight.

In various embodiments, optics may be used to tailor the light intopredetermined optical distributions, thus increasing the efficiency ofthe system. In a some embodiments, the distribution may be tailored tohave a cut off such that above certain angles, there is substantiallylittle light. In various embodiments, a secondary optical accessory maybe used to change the optical distribution, for example, to provideuplight or asymmetrical distributions.

In some embodiments, the LED system may be designed to be less than 4lbs with the capacity to emit greater than 10,000 lumens. In someembodiments, the LED systems may be designed to operate from offline ACvoltage sources. In various embodiments, the LED systems may be designedto operate from a ballast. In some embodiments, the LED systems may bedesigned to operate from offline AC voltage sources. In variousembodiments, the LED systems may be designed to operate from a ballastand from offline AC voltage sources.

Although the technology described is particularly applicable to LEDlamps such as PAR, MR, BR, HID shapes, it can also be applied to buildLED fixtures or more generally any LED systems. In some embodiments, theLED lighting system may replace HID lamps used in high bay or low bayapplications. In some implementations, references to high bay also applyto low bay implementations and vice versa.

In the illustrations and embodiments of this disclosure, the orientationof LED system is shown with LED pointing in a downward orientation sothe air flow from bottom through the LED and/or optics into interior ofthe heatsink and outward through the back of the LED system. However,the orientation may be reversed so the inlet is the back of the LEDsystem and the air outlet is the front of the system. In otherembodiments, the LED system may be of a skewed orientation. As such, theembodiments are not necessarily restricted to any particularorientation.

The details of various embodiments are set forth in the accompanyingdrawings and the description below. Other features and advantages willbe apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A depicts an isometric view of an exemplary LED system.

FIG. 1B depicts an exploded view of an exemplary LED system.

FIG. 2A depicts a front view an exemplary LED embodiment.

FIG. 2B depicts a conceptual view of exemplary opening or open regionsbetween the LEDs.

FIG. 2C depicts a conceptual view of exemplary openings of a LED.

FIG. 3 depicts a rear view of a primary optic having at least one optic.

FIG. 4A depicts a raw light output distribution from an exemplary LED

FIG. 4B depicts a reflector with a reflective surface redirecting atleast a portion of a raw light output from an exemplary LED package.

FIG. 4C depicts a light output distribution of a total internalreflection (TIR) lens.

FIG. 4D depicts a light output distribution of a dielectric CPC.

FIG. 4E depicts a light output distribution of a dielectric CPC with anoutput surface explicitly curved in a convex shape.

FIG. 4F depicts a side view of an LED system having multiple LEDpackages 420 corresponding to one optic.

FIG. 5A depicts a top view of an exemplary primary optic.

FIG. 5B depicts a conceptual view of exemplary opening having at leastthree optics that form an outer perimeter.

FIG. 5C depicts a conceptual view of an exemplary opening within anouter perimeter.

FIG. 6A depicts a polar plot illustrating an exemplary optical intensityfor a Lambertian optical intensity distribution of a raw light outputfrom an LED.

FIG. 6B depicts a plotted Cartesian light distribution where an x-axisis plotted from 0-90°.

FIGS. 6C, 6D, 6E, and 6F illustrate characteristics of various differentoptical distributions.

FIG. 7A depicts a cross section view of an exemplary LED system having aheatsink.

FIG. 7B depicts a front view of an exemplary LED system having the opticremoved for to reveal the LED locations.

FIGS. 8A, 8B, 8C, 8D, 8E, and 8F depict various views of an exemplaryLED system having a heatsink with elongated features.

FIGS. 9A-9B depict various views of an exemplary LED system

FIGS. 10A-10B depict an isometric view and a front view of an exemplaryheat sink having at least two fins.

FIGS. 10C-10D depict an isometric view and a front view of an exemplaryheatsink having fins of different radial lengths.

FIGS. 10E-10F depict an isometric view and a front view of an exemplaryheatsink having an opening in the center.

FIGS. 11A-11B depict an isometric view and a front view of an exemplaryheatsink.

FIG. 11C depicts an exploded view of an exemplary heatsink.

FIGS. 11D and 11E depict an exemplary set of a pair of fins.

FIGS. 12A, 12B and 12C depict an isometric view and a front view of anexemplary optical accessory.

FIG. 13A depicts the front view of an exemplary optical system 101having an optical accessory.

FIG. 13B depicts a cross section view of an exemplary optical systemhaving an optical accessory.

FIG. 13C depicts an illustrative ray trace of a cross section of anexemplary optical system.

FIG. 14 depicts perspective view of an optical accessory.

FIG. 15 depicts a top perspective view of an exemplary optical accessoryhaving an additional optical accessory region 1501 that is used toredirect the light from the interior of corresponding LEDs.

FIG. 16A depicts a schematic of an exemplary 400 W Probe Start MetalHalide ballast designed to work with a probe start M59 Metal Halide lampload.

FIG. 16B depicts a schematic of a 400 W Pulse Start Metal Halide ballastdesigned to work with probe start M135 Metal Halide lamp load.

FIG. 17 depicts a schematic of an exemplary electronic LED driverdesigned to interface with a magnetic ballast.

FIG. 18 depicts a schematic of an electronic LED driver designed tointerface with a magnetic ballast having a bridge, a switch controlledby a controller unit, a smoothing capacitor and a string of LEDs withtotal forward voltage V_(f).

FIG. 19 depicts possible methods by which a controller unit controls aswitch.

FIGS. 20A, 20B, 20C, 20D, 20E, 20F, 20G, 20H, 21A, 21B, 21C, 21D, and21E depict various schematic of an exemplary single LED driverspecifically designed to be able to be power by either a magneticballast or directly with the offline AC source V_(s).

FIGS. 21A, 21B, 21C, 21D, and 21E depict various schematics of anexemplary electronic LED driver designed to be powered by a ballast orto be powered directly with the offline AC source.

FIG. 22 depicts a schematic of an exemplary electronic LED driver usinga fly back topology designed to be powered by a ballast or to be powereddirectly with the offline AC source.

FIG. 23 depicts possible methods by which a controller unit controls aswitch with at least two frequency components.

FIGS. 24A and 24B depict control scheme schematics that allow forimproved power factor and harmonic distortion.

FIG. 25 depicts a process by which the control scheme can determine thetype of power source it is connected to.

Like reference symbols in the various drawings indicate like elements.

ILLUSTRATIVE EMBODIMENTS

FIG. 1A depicts an isometric view of an exemplary LED system. Asdepicted, the LED system is in the form factor of a LED Lamp 100.

FIG. 1B depicts an exploded view of an exemplary LED system. Withreference to FIG. 1A, the LED system includes the following subsystems:a light emitting diode (LED) 101, a heatsink 102, an electronic driver106, a primary optic 103, a secondary optic accessory 104, and anelectronic accessory 105.

Each sub system 101-106, having characteristics, features, permutationsor variations described in further detail below.

LED

The LED referenced in this disclosure is intended to be very general innature. The LED includes at least one light emitting semiconductor dieand, optionally, packaged with phosphor or integral optic or externaloptic or mounted on to a PCB.

The LED having at least a portion of its spectrum emitting in the range250 nm to 900 nm, such as, for example, UV, visible or infrared regions.

The LED may be packaged in a format that allows for mounting to a PCB.The PCB material, such as, for example, fiber glass resin material(e.g., FR4) or a metal core printed circuit board (MCPCB), may haveimproved thermal dissipation characteristics. The LED package may be asurface mountable device (SMD), chip on board (COB) or chip scalepackage (CSP) or other well know packaging methods.

In the event where there are at least two LEDs, the LEDs may havesubstantially similar spectrums or substantially dissimilar spectrums.For example, different spectrums may include a color that is red,orange, yellow, green, blue, indigo, violet, ultra violet or infra-redor different color temperatures of white.

FIG. 2A depicts a front view an exemplary LED embodiment. With referenceto FIG. 1B, LED 101 includes one hundred and forty-four LED packages 201mounted to a printed circuit board (PCB) 202. The LEDs are arranged inan inner ring or perimeter 221, a middle ring or perimeter 222 and anouter ring or outer perimeter 223. The middle perimeter 222 does notcross the outer perimeter 223. The inner most perimeter 221 does notcross the middle perimeter 222. The word ring and perimeter are usedinterchangeably. As depicted, the outer ring has more LEDs than theinner ring. The inner ring 221 having twenty-four LED packages, themiddle ring 222 having forty-eight LED packages, and the outer ring 223having seventy-two LED packages. The outer ring 223 encircling,encompassing, enclosing or containing all the LEDs as well as the middlering 222 and inner most ring 221. The middle ring 222 containing theinner ring 221. At least one open region 205 a is contained between themiddle ring 222 and the outer ring 223. At least one open region 205 bis contained between the inner ring 221 and the middle ring 222. Atleast one open region 205 c is contained within the inner ring 221. Theopen regions 205 a, 205 b and 205 c may allow for air flow.

Spreading the LEDs across multiple rings may provide advantages over asingle ring containing all the LEDs or if all the LEDs were concentratedin a central region. The placing of LEDs across multiple rings mayenable the LED to be thermally distributed more evenly across thesurface contained within the outer perimeter and thereby lower thermalwhile enabling more LEDs to be disposed on the surface. In variousembodiments, the LED may include at least one opening between the ringsof LEDs.

FIG. 2B depicts a conceptual view of exemplary opening or open regionsbetween the LEDs. As depicted, a LED (e.g., the LED 101) includes atleast 3 LEDs 207-209, each LED 207-209 mounted on a printed circuitboard (PCB) 211-213, respectively. The PCBs 211-213 may be mechanicallyisolated or mechanically connect to each other. For example, the dottedlines may represent PCB, or other material, that mechanically connectsto at least two of the PCB 211-213. An outer perimeter 216 is formed bythe outer LEDs 207-209. The outer perimeter 216 containing,encompassing, encircling, or containing all the LEDs in the system. ThePCB open region 221 is formed within the outer perimeter 216 and betweenthe PCBs 211-213 allowing for air to flow between the LEDs.

FIG. 2C depicts a conceptual view of exemplary openings or open regionsbetween the LEDs. With reference to FIG. 2B, the LED further includes aninner perimeter 226 contained within the outer perimeter 216. Asdepicted, the inner perimeter is formed by three LEDs 227-229. Each LED227-229 mounts on a PCB 231-233, respectively. At least one of the LEDs227-229 forming the inner perimeter 226 may be different than the LEDs207-209 forming the outer perimeter 216. The outer perimeter 216 and theinner perimeter 226 do not cross each other. The outer perimeter 216encloses the inner perimeter 226. The PCBs 227-229 may be mechanicallyisolated or mechanically connect together. For example, the dotted linesmay represent PCB, or other material, that mechanically connects atleast two of the PCBs 227-229. The inner perimeter 226 contains at leastone inner open region 225 that allows for air flow between the LEDs. Theinner perimeter 226 is completely contained by the outer perimeter 216.The addition of the inner perimeters 226, with optics (not shown),allows for the LEDs, and thus the LED generated heat, to be optimallyspread across a surface defined and bounded by the outer perimeter,allowing for improved heat dissipation resulting and a more eventemperature distribution across the heatsink surface.

In various embodiments, at least one of the LEDs 227-229 may be mountednear the edge or near the perimeter of the mechanics that comprise theLED optical system. In some embodiments, the LEDs 227-229 may be mountedwithin 25 mm of the edge of the optical system. With reference to FIGS.1B-2B, the outer ring of the LED 223 is mounted within 25 mm of thediameter edge of the heatsink 102.

Primary Optic

The primary optic redirects at least a portion of light from at leastone LED into a first optical distribution. The type of optic is intendedto be very general and may accomplish the redirection of light throughmechanisms such as reflection or refraction or combinations thereof.Reflective or refractive elements may include convex lens, concave lens,air compound parabolic reflector (air CPC), dielectric compoundparabolic reflector (dielectric CPC), Fresnel lens, total internalreflection lens (TIR), gradient index lens, diffractive lens, microlenses, micro structures, diffractive optics, segmented lens, RXI lens,light guide or light guide taper or combinations thereof. The primaryoptic may consist of a single optic or an array of optics.

In some embodiments, the LED system may include at least three LEDs,each LED having its own optic. Within an outer perimeter formed by theat least three LEDs, at least one open region may be formed within theoptic and LEDs that allows for improved air flow when compared to anopen region that is blocked.

In some embodiments, the LED system 101 has at least three LED packagesand at least one optic. The optic may be shared by the LEDs. The opticmay have an open region. An outer perimeter formed by the at least threeLEDs includes at least one open region. The open region for the opticand the LEDs may allow for improved air flow. In an illustrativeexample, the optic may be a reflector, such as, for example, a prismaticreflector, a mirror, or an aluminum metal reflector. Such reflectorstructures may have an open structure that allows for air flow.

FIG. 3 depicts a rear view of primary optic having at least one optic301. With reference to FIGS. 1A-3, each optic 301 corresponds to atleast one LED package 201 of the LED 101. The optic 301 redirects atleast a portion of the raw light output, from at least one LED package201, into a first optical distribution. As depicted, there are onehundred and forty-four optics 301. The optics 301 are arranged such thatan inner ring 321 of twenty-four optics corresponds to the LED packages201 of the inner ring 221, a middle ring 322 of forty-eight opticscorresponds to the LED packages 201 of the middle ring 222, and an outerring 323 of seventy-two optics corresponds to the LED packages 201 ofthe outer ring 223. The individual optics 301 are held together by aholder 302 to form a common mechanical unit held together for ease ofassembly. The material for the optics may be substantially opticallytransmissive and include material such as acrylic, polycarbonate orglass. If the material is plastic, the material may be fabricated usinginjection molding or compression molding techniques.

FIG. 4A depicts a raw light output distribution from an exemplary LED.As depicted, a raw light output 402 from an exemplary LED package 401tends to be substantially Lambertian in distribution with a full widthhalf maximum beam angle (FWHM) of about 120 degrees (120°). The purposeof the primary optic is redirect at least a portion of this raw outputinto an overall first optical distribution. In some embodiments, thefirst optical distribution has a FWHM<120°, for example FWHM<100° orFWHM<90°.

FIG. 4B depicts a reflector with a reflective surface redirecting atleast a portion of a raw light output from an exemplary LED package. Thetotal resulting light includes redirected and un-redirected light whichform a first optical distribution 403. A reflective surface 404 may beformed by a metal coating on to a substrate material of appropriateshape to reflect the incident light into at least a portion of the firstoptical distribution. In such a case, since the light does not penetratethe substrate material, the substrate material needs not be opticallytransmissive. In some embodiments, at least a portion of the reflectivesurface 404 may be substantially in the shape, or based on the shape, ofa compound parabolic concentrator (CPC).

FIG. 4C depicts a light output distribution of a total internalreflection (TIR) lens. Input refractive surfaces 406, 407 refract atleast a portion of the raw light output 402 from the LED 401. At least aportion of the light refracted by input surface 407 is further refractedby exit surface 409. At least a portion light refracted by input surface406 is reflected by TIR surface 408 and then refracted by exit surface409. The total resulting light forms a first optical distribution 410.

FIG. 4D depicts a light output distribution of a dielectric CPC. Aninput surface 412 refracts at least a portion of the raw light output402 from the LED 401. At least a portion of the light refracted by theinput surface 412 is further refracted by an exit surface 414. At leasta portion of the light refracted by the input surface 412 is furthertotally internally reflected by a surface 413 and then refracted by anexit surface 414. The total resulting light forms a first opticaldistribution 415. In an illustrative example, the surfaces 414, 412 aresubstantially flat. In some embodiments, at least a portion of either ofthe surfaces 414, 412 are curved.

FIG. 4E depicts a light output distribution of a dielectric CPC with anoutput or exit surface explicitly curved in a convex shape. As depicted,a first optical distribution 417 results from an output surface 416being explicitly curved in a convex shape. The output surface 416 mayadvantageously reduce wide angle rays in the first optical distribution415 to a distribution 417 with less wide angle light. The resultingdistribution 417 may reduce glare.

FIG. 4F depicts a side view of an LED system having multiple LEDpackages corresponding to one optic. As depicted, an optic 421 is sharedby at least three of the LEDs 420 (third LED not shown). The optic 421having an open region 422. Within an outer perimeter, formed by at leastthree LEDs 420, includes an open region 425. In various embodiments, theouter perimeter may include multiple open regions. The open region 425,as formed by the optic 421 and the LEDs 420 may allow for improved airflow 423, 424. For example, the optic 421 may be a reflector, such as,for example, a prismatic reflector, or a coated mirror, or an aluminummetal reflector. Generally, such reflectors are open structures topermit air to flow freely.

FIG. 5A depicts a bottom view of an exemplary primary optic. Withreference to FIGS. 1 and 3, the LED system 101 includes an outerperimeter 501 formed from 72 outer optics 301. The outer perimeter 501encompasses all remaining optics 301. All one hundred and forty-fouroptics 301 are joined together by a holder 302 to form a commonmechanical unit. As depicted, the LED system 101 includes an outer ring501, a middle ring 510 and an inner ring 511. Each ring 501, 510-511having a plurality of LEDs. The outer ring 501 containing both themiddle ring 510 and the inner ring 511. The middle ring 510 containingthe inner ring 511. The ring 501 having at least one optic open region502 a. The ring 510 having at least one optic open region 502 b. Thering 511 having at least one optic open region 502 c. The open regions502 a-502 c allow for air flow.

FIG. 5B depicts a conceptual view of exemplary opening in the optichaving at least three optics that form an outer perimeter. At leastthree optics 503-505 form an outer perimeter 506 such that the outerperimeter 506 contains, encircles, or encompasses any remaining opticsin the LED system (e.g., LED system 101). The optics 503-505 may bemechanically isolated or mechanically connect together. For example, thedotted lines may represent portion of a lens holder that mechanicallyconnects at least two of the optics 503-505. Each optic 503-505corresponds to an LED package (e.g., LED package 201). The optic openregion 508 is formed within the perimeter 506 between the optics503-505. The optic open region 508 may allow for air flow.

FIG. 5C depicts a conceptual view of an exemplary opening within anouter perimeter. With reference to FIG. 5B, a second inner perimeter 526formed by an inner at least three optics 523-525 is contained within theouter perimeter 506. In some embodiments, at least one of the LEDscorresponding to at least one of the optics 523-525 is different than atleast one of the LEDs corresponding to at least one of the optics503-505. Each optic 503-505, 523-525 corresponds to an LED package. Asdepicted, the outer perimeter 506 and the inner perimeter 526 do notcross each other. The optics 523-525 may be mechanically isolated ormechanically connected together. For example, the dotted lines mayrepresent a portion of a lens holder that mechanically connects at leasttwo of the optics 523-525. The inner perimeter 526 includes at least oneinner open region 528 to allow airflow. The inner perimeter 526, asdepicted, is completely contained within the outer perimeter 506. Theaddition of the inner perimeter 526, with optics, allows for the LEDs tobe optimally spread out across the surface defined and bounded by theouter perimeter 506 thus allowing for improved heat dissipationresulting in a more even temperature distribution across the heatsinksurface.

In some embodiments, at least one optic may be mounted near theperimeter of the mechanics that compose the overall optical system. Invarious embodiments, at least a portion of the optic may be mountedwithin 25 mm of the edge of the LED system. With reference to FIGS. 2Aand 3A, the outer ring 323 of optics, corresponds to the outer ring 223of LEDs. The outer ring 323 may be mounted within 25 mm of the diameteredge of the heatsink 102.

Optical illuminous intensity distribution or optical light distributionis measured in how light is emitted at different angles from a lightsource. The total possible distribution is into a sphere, also known asfour PI steradians (4π). A typical unit for visible light intensity iscandela (cd) or lumens (l) per steradians. A typical representation ofthe light distribution is to slice through the sphere and plot the lightintensity in the form of a polar plot where the radial units are incandela.

FIG. 6A depicts a polar plot illustrating an exemplary optical intensityfor a Lambertian optical intensity distribution of a raw light outputfrom an LED. A LED emits a light 601 substantially into the lowerhemisphere. A center optical axis 602 is at zero degrees) (0° on thepolar plot. For directional lighting applications including high bay,low bay, PAR, MR, BR, AR, the majority of light is intended toilluminate a useful area in front of the optical system in direction ofthe optical axis 602. A Useful Region of light 603 is defined as ±50°from the center optical axis 602. The region above ±50° but below ±90°is defined as the Glare Zone 604. For the Lambertian distribution,significant light may be in the Glare Zone 604 which is not only wastedbut a source of visual discomfort. It is highly desirable to minimizelight emitted into the Glare Zone 604 and more efficiently redirect, viaan optic, this light into the Useful Region 603. The Useful Region 603and the Glare Zone 604 form the lower hemisphere where the majority oflight is generally emitted into. The upper hemisphere 605 defines aregion called Uplight Zone 605. The Uplight defines how well a light mayilluminate the ceiling. In various embodiments, Uplight may or may notbe required.

FIG. 6B depicts a plotted Cartesian light distribution where an x-axisis plotted from 0-90° to show the optical intensity distribution in onlyone hemisphere.

The illuminance profile E(θ), at a plane of interest, is calculated by

${E(\theta)} = \frac{{I(\theta)} \cdot \left( {\cos \; \theta} \right)^{3}}{h^{2}}$

where an intensity distribution I(θ) in candela at angle θ and h equalsthe height from the luminaire to a plane where the illuminance is to becalculated. The plane, for example, may be a work surface or a floor.One unit for illuminance is lumens per meter square (l/m²) or lux. Notethe illuminance E(θ) from equation

$\frac{{I(\theta)} \cdot \left( {\cos \; \theta} \right)^{3}}{h^{2}}$

declines rapidly with (cos θ)³. In order to have a more evenlyilluminance E(θ), optical intensity distribution I(θ) needs to at leastpartially compensate by increasing in value with θ to counteract thedecreases with (cos θ)³. In some embodiments, this compensation in I(θ)manifest itself as a peak of the optical intensity distribution I(θ)away from the center axis to an off axis region 15-45°. In variousembodiments, the optical intensity results in a relative illuminanceprofile such that the variation, from center to a relative lateraldistance of 0.7 from center, may be at least 40% of the centerilluminance. Relative lateral distance is defined as the lateraldistance D from the center axis 602 divided by height h, where thelateral distance is D=h·tan θ, and the height h of the LED system Assuch, the relative lateral distance is simply tan θ.

The optical distribution created by at the at least one LED incombination with at least one optic may determine parameters such asglare, amount of light in the Useful Zone, Uplight, relative illuminanceuniformity and level or illuminance. In various embodiments, the opticaldistribution may satisfy one or more of the following requirements:

-   -   a. The peak of the optical intensity distribution I(θ) is not at        the center axis but in a region 15°−40° from center.    -   b. The optical intensity I(θ) results in a relative illuminance        profile such that the variation, from center to a relative        lateral distance of 0.7 (tan θ=0.7), is at least 40% of the        center illuminance.    -   c. At least 85% of the total light in the lower hemisphere is in        the useful zone.    -   d. No more than 20% of light is in the glare zone.    -   e. The maximum candela in the glare zone 604 is no more than 15%        of the center axis 602 candela.    -   f. At least 70% of the total light is in the useful zone 603 and        at least 7.5% of light is in the up light zone.    -   g. At least 5% light is in the Uplight zone.

FIGS. 6B-6F illustrate characteristics of various different opticaldistributions. The first optical distribution from an existing AcuityHID 400 W fixture. The second optical distribution illustrates anexample of an LED Lambertian distribution. The third opticaldistribution from an LED Gaussian distribution. The fourth opticaldistribution from an exemplary LED target distribution. Thecharacteristics of these optical distributions are also summarized inTables 1 to 3.

TABLE 1 Luminaire Lamp Fixture Light Loss Net System Lumens EfficiencyFactor Lumens Acuity HID 40,000  70% 63% 17,640 LED Lambertian 18,000100% 85% 15,300 LED Gaussian 18,000 100% 85% 15,300 LED Target 18,000100% 85% 15,300

TABLE 2 Luminaire % Light in % Light in Lumens in Lumens in SystemUseful Zone Glare Zone Useful Zone Glare Zone Acuity HID 78.5% 21.5%13,841 3,799 LED Lambertian 60.3% 39.7% 9,225 6,075 LED Gaussian 72.6%27.4% 11,115 4,185 LED Target 99.7%  0.3% 15,260 40

TABLE 3 Center Relative Max Center Lux Lux Variation Luminaire CandelaCandela in @ 0° from Center System @ 0° Glare Zone (20 ft Height)(0-0.7) Acuity HID 6915 69.8% 186 56% LED Lambertian 4740 64.3% 128 45%LED Gaussian 7661 33.0% 206 32% LED Target 7662  6.9% 206 59%

The first optical distribution is an existing commercial luminaire,Acuity High Bay HID (THD 400MP A15 TB LPI) system. This Acuity HIDfixture is used for reference to compare the later three LED systems. Assummarized in Table 1, the Acuity HID fixture uses an HID lamp with aninitial 40,000 lumens and a reflector with a 30% loss that is used toredirect the light. As such, the Acuity HID has fixture efficiency of70%. In addition, the Acuity HID Fixture has a light loss factor of 63%.Light loss factor accounts for other loss issues, such as, for example,lamp lumen depreciation or dirt accumulation. Generally HID systems havea much higher lumen degradation than LED systems resulting in the HIDhaving a worse light loss factor, at 63%, than an LED system, at 85%.The net lumens after fixture efficiency and the light loss factor is17,640 lumens. The Acuity HID optical distribution 610, as depicted inFIG. 6B, is calculated based on 17,640 lumens. FIG. 6F depicts thecumulative integrated light from on center axis 602 to various anglesand provides an indication of the total light in various zones. In thecase of the Acuity HID Fixture, FIG. 6F and Table 2, illustrate that theAcuity HID optical distribution 650 has about 78.5% in the Useful Zone603 while 21.5% of the energy is wasted in the Glare Zone 604. As such,only 13,841 lumens are in the Useful Zone 603 while 3,799 lumens arewasted in the Glare Zone. FIG. 6C depicts the optical distributionnormalized to a center value. As depicted, the HID normalized opticalintensity distribution curve 620 shows that the maximum candela in theGlare Zone 604 is at very high 69.8% of the center candela value. FIG.6D depicts a calculated illuminance in lux at a height equal to 20 feet(h=20). The X-axis is the relative lateral distance from center axis 602and is calculated as lateral distance divided by the height, or simplytan θ. The HID illuminance 630, corresponding to Table 3, illustrates acenter peak of about 186 lux. FIG. 6E depicts the relative illuminance640 uniformity normalized to the center axis illuminance. FIG. 6E, andTable 3, illustrate the curve 640 showing the HID optical distributionresults in a worst case of a relative illuminance of 56% at relativelateral distance of 0.7.

The second optical distribution is an example of a LED system withsubstantially Lambertian distribution 611 (reference FIG. 6B). Such adistribution is typical of a raw LED emission without redirection withan optic. The raw LED output is 18,000 lumens. Accounting for an afterthe fixture efficiency of 100% and a light loss factor of 85%, the netlumens are reduced to 15,300 lumens. The optical distribution of 611 isadjusted to reflect 15,300 lumens. With reference to Table 2 and thecumulative light curve 651, the Lambertian optical distribution 611 hassignificant glare with about 39.7% of light (6,075 lumens) wasted in theGlare Zone 604 and only 60.3% (9,225 lumens) in the Useful Zone 603. Theresulting illuminance 631, with reference to FIG. 6D and summarized inTable 3, has center value of 4740 lux which is significantly lower thanthe reference case of the Acuity HID of 6915 lux. The Lambertiandistribution relative intensity 621, with reference to FIG. 6C andsummarized in Table 2, shows a relative maximum candela of 64.3% in theGlare Zone 604 relative to the center intensity. The curve 641, withreference to FIG. 6E and summarized in Table 3, illustrates theLambertian optical distribution results in a worst case of a relativeilluminance of 45% at relative lateral distance of 0.7.

The Gaussian optical intensity profile is intended to represent a broadclass of intensity profiles. The profile need not to be exactly Gaussianin shape but rather any optical distributions with a peak intensitysubstantially near a center optical axis of 0° then declining inintensity with higher angles, i.e. moving away from the center opticalaxis 602. Such an optical intensity distribution I(θ) cannot compensatefor the (cos θ)³ fall off resulting in an illuminance profile that isgenerally not very uniform. Broadening the Gaussian cannot compensatefor (cos θ)³, and may simultaneously lead to very high glare andsignificant reduction on axis illuminance. The Gaussian like shapes maytypically be created with simple optics, such as, for example, simplelens, TIR, or simple reflectors.

With reference to FIG. 6B and Table 1, the third optical distribution612 is an example of a LED Gaussian distribution that has been adjustedto reflect 15,300 lumens based on a total of 18,000 lumens discounted byan 100% fixture efficiency and an 85% light loss factor. The Gaussianshape and FWHM was further determined by setting the center peak to 7661cd to match the fourth distribution 633. Although the total lumens inthis example are the same as the Lambertian distribution, the centerpeak intensity of 7661 cd is higher than both the Lambertian and theAcuity HID. However, the cumulative light curve 652 (reference FIG. 6Fand Table 2) shows a relatively high glare of 27.4% of the total lightin the Glare Zone 604. This results in 11,115 lumens in the Useful Zone603 and 4,185 lumens in the Glare Zone 604. Also, the relative candelacurve 622 (reference FIG. 6C and Table 3) shows a relative maximumcandela of 33% in the Glare Zone 604. Although the portion of glarelight and maximum candela in Glare Zone 604 may be improved over boththe Acuity HID and the Lambertian, the glare is still relatively high.In addition, the improvement in glare comes at the expense ofilluminance uniformity. The illuminance curve 632 (reference FIG. 6D andTable 3) shows a center illuminance of 7661 lux, but the variation inilluminance 642 from center to a relative lateral distance of 0.7 isabout 32% which is worse than both the Acuity HID and the Lambertian.

FIG. 6B depicts a Target LED optical distribution 613 that has beenadjusted to reflect 15,300 lumens based on a total of 18,000 lumens inaccordance with a 100% fixture efficiency and an 85% light loss factor.Optical distribution 613 illustrates a general class of profiles thatrepresents a preferred embodiment of the optical distribution. Thisclass of profiles simultaneously provide an improved lower glare and animproved illuminance uniformity. The characteristic may be accomplishedby partially compensating for the (cos θ)³ illuminance fall off byincreasing the optical intensity distribution I(θ) with angle θ, forcertain range of angles. This results in a peak intensity away from acenter axis in a region about 15-45° from center. The particulardistribution 613 has a peak intensity at about 24°. Anothercharacteristic, the intensity minimizes glare by bringing opticaldistribution down from the peak to a relatively low value in the GlareZone 604. This requires a much steeper roll off in intensity than may becharacteristic of either the Lambertian or the Gaussian IntensityDistribution. With reference to FIG. 6C and summarized Table 3, therelative intensity 623, as depicted, is less than 6.9% in the Glare Zone604 from a peak of about 115% at 24°. This steep roll off occurs within26°. The result is the cumulative light level curve 653, as depicted inFIG. 6F and as summarized in Table 2, results in about 99.7% (15,260lumens) of the total light in the useful zone with only 0.3% of thelight in Glare zone (40 lumens). The glare may therefore be asignificant improvement over optical distribution of Acuity HID,Lambertian or Gaussian. At the same time, as depicted in FIG. 6D, theilluminance profile 633 is significantly higher over a relative lateraldistance 0.7 starting with a center illuminance is 206 lux. In addition,the variation in illuminance from center to a relative lateral distanceof 0.7 is about 59% of the center illuminance. Thus, of the fourdistributions, the Target distribution not only has the lowest glare butalso the highest center candela, the highest illuminance, the highestcenter illuminance and the best illuminance uniformity. The LED Targetoptical distribution of 613, with only a raw 18,000 lumens,significantly out performs the legacy Acuity HID fixture with more thantwice the raw light level at 40,000 lumens.

In some embodiments, the characteristics of the Target optical intensitydistribution is preferably achieved using the dielectric CPC opticdepicted in FIG. 6D or the dielectric CPC optic with the curved outputdepicted in FIG. 6E.

In some embodiments, the first optical distribution or the Targetdistribution, satisfies one or more of the following requirements:

-   -   a. The peak of the optical intensity distribution I(θ) is not at        the center axis but in a region 15°-45° from center.    -   b. The optical intensity distribution I(θ) results in a relative        illuminance profile such the variation in illuminance from        center to a relative lateral distance of 0.7 is at least 40% of        the center illuminance.    -   c. At least 85% of the total light in the lower hemisphere is in        the useful zone 603.    -   d. No more than 20% of light in the glare zone 604.    -   e. The maximum relative intensity in the glare zone 604 is no        more than 15% of the center intensity.

Heat Sink

Heatsinks can be fabricated by multiple processes well known in thearts, such as, for example, diecasting, extrusion, skiving, folded fin,and sheet metal. The heat sink material may include aluminum, aluminumalloys, copper, copper alloys or a thermally conductive plastic. Suchthermally conductive plastic can be fabricated from processes such asinjection molding that have a thermal conductivity greater than 1 W/M-K.One company that supplies such thermally conductive plastic material isCelanese Corporation. Generally, heatsinks are constructed with a regionof elongated features that have a large surface area composing offeatures such as pins or fins attached to a common base. The largesurface area may be used to dissipate heat from the heatsink to the air.These elongated features are generally mechanically held together byattaching them to a common base. In some of the embodiments of thisdisclosure the base is substantially planar and serves as a mechanicalstructure where the LEDs and/or Optics are attached.

FIG. 7A depicts a cross section view of an exemplary LED system having aheatsink. A LED system includes a heatsink 701, at least 3 LEDs 702, anda series of optics 703 that correspond to the LEDs 702. The LED 702 arein thermal and mechanical contact with heat sink 701. The heatsink 701has a series of elongated features 704, such as fins or pins, todissipate the heat generated from the LED 702 to the ambient air. Theseelongated features 704 are mechanically attached to the heatsink base706 that is substantially planar. The heatsink 701 having at least oneopening such as 712 or 705. At least three of the outer LEDs 702 formingan outer perimeter 711. The series of optic 703 have at least oneopening 713, 707. The openings 713, 707 at least partially overlap atleast one opening 705, 712 in the heatsink base 706. Together theseopenings enable direct and unimpeded airflow flow along from the frontof the LED system to the interior of the elongated regions 708-709 ofthe heatsink 701 and thereby improve thermal dissipation.

FIG. 7B depicts a front view of an exemplary LED system having the opticremoved for to reveal the LED locations. As depicted, at the LED systemincludes at least one inner perimeter 721 formed by at least 3 LEDs 720.At least one of the LEDs 720 forming the inner perimeter 721 may bedifferent than the LEDs 702 forming the outer perimeter 711. The innerperimeter 721 does not cross cover the outer perimeter 711. As depicted,the outer perimeter 711 encloses the inner perimeter 721. Within theinner perimeter 721, there is at least one opening, such as 712, thatallows for improved air flow.

Without such openings 705, 707, 712-713 or open regions 708-709, the airwould need to take an indirect path by flowing from front of theheatsink 701 around the edge of the heatsink 701 and then back towardsthe interior 709 of the heatsink 701. This indirect circuitous routeincreases air flow resistance resulting in decreased air flow, and theprocess of flowing around the heatsink 701 heats up the air such that bythe time the air reaches the interior 709 of the heatsink 701 there maybe significantly less cooling capacity. The openings 705, 707, 712-713therefore allow for substantially direct and improved airflow of coolair to the interior of the heatsink elongated region 704 resulting insignificantly improved thermal resistance.

The air flow also exits 730 the elongated features directly above theelongated features thus enabling the air to flow in a low air resistancepath that is substantially in a vertical axis from the front of the LEDsystem to exit behind the LED system.

At least one opening 705, 707, 712-713 or open regions 708-709 improveair flow and satisfy at least one of the following criteria.

-   -   a. The opening region in the heatsink base, optic and PCB is at        least 25% of the outer perimeter area.    -   b. The improved air flow decreases thermal resistance by at        least 5%, 10% or 20% than if such openings 705, 707, 712-713        were covered up.    -   c. The improved air flow reduces the average temperature of the        heatsink by at least 5° C. than if such openings were covered        up.    -   d. The improved air flow reduces the maximum temperature of the        heatsink by at least 5° C. than if such openings were covered        up.    -   e. The air flows in a substantially vertical flow path from the        front of the optical system through the heatsink base into the        elongated features and exiting directly above the elongated        features.

FIGS. 8A-8F depict various views of an exemplary LED system having aheatsink with elongated features. FIG. 8A depicts an isometric view.FIG. 8B depicts an explode view with an optic removed at a distance.FIG. 8C depicts a front view of a LED system with an optic removed toshow at least three LEDs. FIG. 8C depicts a front view of the optic.FIG. 8E depicts the front view of the LED system. FIG. 8F depicts across section L-L of the LED system referenced to FIG. 8E. A LED system800 includes a heatsink having a series of pins 803, a heatsink base802, at least three LEDs 804, an array of optics 820. The array ofoptics 820 consisting of at least three optics 824 that correspond tothe at least three LEDs 804. At least three of the outermost LEDs 804form an outer perimeter 809 from which all the LEDs 804 are contained.Within the outer perimeter 804 there is at least one opening 806-805,808 that allows for improved airflow. At least three of the outermostoptics 824 form an outer perimeter 829. Within the outer perimeter 829there is at least one opening 826-825, 828 to allow for improvedairflow. Each optic 824 corresponds to an individual LED 804. Optics 824redirect at least a portion of the raw light output from itscorresponding LED 804 into a first optical distribution. The LEDs 804and optics 824 are described in other parts of this disclosure. Theopenings in the heatsink 806-805, 808 at least partially overlap some ofthe openings 825-826, 828 in the optic 824. For example, as depicted inFIGS. 8E and 8F, the heatsink opening 806 at least partially overlapsthe optic opening 826, the heatsink opening 805 at least partiallyoverlaps the optic opening 825 and the heatsink opening 811 at leastpartially overlaps the optic opening 821. Together these openings805-806, 808, 825-826, 828 allow for improved and more direct verticalairflow path 831,832 from the front 830 of the LED system 800 to theinterior of the heatsink elongated features 803 and exiting 840 abovethe elongated features. The illustrated geometry may allow for the airto flow almost directly and unimpeded from front 830 of the system tothe elongated pin feature 803 at the interior 831,832 of the heatsink.

In various embodiments, the outer LED perimeter 809 includes at leastone inner perimeter 810-811, each inner perimeter 810-811 is formed byat least three LEDs 804. At least one of the LEDs 804 forming the innerperimeter 810-811 is different than the at least three LEDs 804 formingthe outer perimeter 809. The inner perimeters 810-811 have at least oneopening 806,808 that allow for improved air flow. The inner perimeters810-811 do not cross over the outer perimeter 809 and are enclosed bythe outer perimeter 809. Within the outer optic perimeter 829, at leastone inner perimeter 820-821 is formed by at least three optics 824. Atleast one of the optics 824 of the least three optics 824 forming theinner perimeter 820-821 may be different than at least three optics 824forming the outer perimeter 829. The inner perimeters 820-821 have atleast one opening 826, 828 to allow for improved air flow. If these suchopenings 826, 828 are blocked, the air 832 has to flow from front of theheatsink around the edge of the heatsink and then back towards theinterior of the heatsink. This indirect circuitous route increases airflow resistance resulting in decreased air flow. This process of flowingaround the heatsink base 802 heats up the air such that by the time theair reaches the interior of the heatsink there may be significantly lesscooling capacity. The LEDs 804, as depicted in FIG. 8C, aresubstantially evenly distributed across the surface of the heatsink base802 thus allowing for improved spreading of the heat load. The openingsin the heatsink base 802 are also substantially evenly distributedacross the surface of the heatsink thus allowing for a more even airflow into the interior of the heatsink. One consequence of more evenlydistributing heat load across the heatsink base is the requirement tospread or conduct the heat across the heatsink base is substantiallyreduced. Rather much of the heat generated by the LEDs may directlyconducted backwards to the heat dissipating features without the needfor spreading across the base. In some embodiments, the lateral heatspreading across the surface of the base is substantially negligible.The reduced heat spreading requirement of the base i.e. reducedrequirement for in plane lateral thermal conductivity allows for thebase to be thin and allow for perforation in the heatsink base 802 withopenings which reduces weight and improve air flow. In some embodiments,the heatsink base may be from 0.5-4 mm in thickness. In FIGS. 8A-8F, TheLEDs 804 are substantially thermal isolated from each other across thebase of the heat sink base 802 and base is only connected by thinslivers 831 between the opening 808 that serves to hold the base as onesingle mechanical unit than for thermal conductivity across the base.

In certain applications, there may be a weight limit for the overall LEDsystem. For example, Underwriters Laboratory (UL) standard 1993,“Self-Ballasted Lamps and Lamp Adapters” Section 5.4 limits the maximumweight up to 1.7 kilograms (kg) for LED Retrofit lamps intended toreplace HID lamps with an E39 socket. Such Retrofit Lamps have beendescribed, for example at ([00182]), in U.S. application Ser. No.14/952,079, titled “LED LIGHTING,” filed by Frank Shum, on Nov. 25, 2015and at FIG. 29-30, of U.S. Provisional Application Ser. No. 62/141,010,titled “LED Lighting,” filed by Frank Shum, on Mar. 31, 2015, the entiredisclosures of which are hereby incorporated by reference. Generally,the heatsink may be a significant portion of the weight of an LEDsystem. The LED system also includes the weight of the driver, optics,and driver housing, for example. The heatsink must therefore weighsubstantially less than 1.7 kg. In some embodiments, the heatsink weighsless than 1 kg while still being capable for dissipating heat from anoptical system generating more than 10,000 lumens. The fabricationprocess such as die casting or extrusion may require a minimum featuresize and or aspect ratio. For example, both die casting and extrusionmay have difficulty in fabricating features sizes less than 1 mm orhaving aspect ratio greater than 10 to 1. The dimensions, and thereforeweight, of the heatsink dissipating features, such as fins or pins, maybe determined by a fabrication limitation rather than requirements forheat dissipation. As such, the heatsink may be heavier than necessary.

In some applications where weight may be critical, sheet metal fins maybe preferred. Sheet metal can achieve a thickness less than 1 mm, less0.6 mm or less than 0.5 mm while simultaneously achieving an aspectratio great than 20 to 1, or 40 to 1 or 80 to 1.

FIGS. 9A-9B depict various views of an exemplary LED system having sheetmetal fins. An LED system 906 includes a heatsink having a series ofheat transfer members such as elongated sheet metal fins 901 attached toa heatsink base 902. At least three of the LEDs 903 are in thermalcommunication with the heatsink. As depicted, the outer LEDs 903 form anouter perimeter 904. The outer perimeter 904 includes at least oneopening 905 to allow for improved air flow from the front 906 of LEDsystem to the interior 907 of the heat sink. In some embodiments, theLED system includes at least one inner perimeter 914 formed by at least3 LEDs 903. At least one of the LEDs 903 forming the inner perimeter 914is different than the LEDs 903 forming the outer perimeter 904. The atleast one inner perimeter 914 does not cross over the outer perimeter904 and is enclosed by the outer perimeter 904. The inner perimeter 914includes at least one opening 915 to allow for improved andsubstantially direct and vertical air flow from the front 906 of LEDsystem to the interior 907 of the elongated fins and exiting above theelongated fins 910.

FIGS. 10A-10B depict an isometric view and a front view of an exemplaryheat sink having at least two fins. A heat sink includes at least twofins 1001, 1006, which are substantially the same size, pointingradially to a common center and are in thermal contact to a base 1002.At least one of the fins 1001, 1006 thermally and mechanically attachesto a center column 1011. At least three of the outer most LEDs 1003,form an outer perimeter 1004 having at least one opening 1005 formedbetween the combination of LEDs 1003, the PCB and the optic to allow forimproved air flow. The optional optic and the PCB are not shown. Asdepicted, the spacing between the fins 1001, 1006 at a heat sinkperimeter 1009 is larger than the spacing of fins near the center region1008. In such a radial arrangement, optimum spacing may be generallydifficult to achieve. For example, if fin spacing at the perimeter 1009is optimized, the fin spacing near the center region 1008 becomes tooclose (e.g., <3 mm) to allow for effective air flow. In someembodiments, at least one of the LEDs 1003 forming the inner perimeter1014 may be different from the LEDs 1003 forming the outer perimeter1004. The inner perimeter 1014 does not cross over the outer perimeter1004 and is enclosed by the outer perimeter 1004. The inner perimeter1014 includes at least one opening 1015 that allows for improved airflow.

FIGS. 10C-10D depict an isometric view and a front view of an exemplaryheatsink having fins of different radial lengths. As depicted, amodification is made to improve the spacing issue by using fins of atleast two different radial lengths with a first fin 1001 with a firstradial length and a second fin 1010 with a shorter radial length. Theshorter fins 1010 are positioned towards the outer perimeter 1004. Inthis configuration, the interior fin spacing 1018 is substantiallyimproved over the center region 1008 while the fin spacing at theperimeter 1009, 1019 remain substantially unchanged.

FIGS. 10E-10F depict an isometric view and a front view of an exemplaryheatsink having an opening in the center. As depicted, a heatsinkincludes an opening 1012 in the center to allow for further improvedairflow.

In FIGS. 10A-10F, the portion of the heatsink base 1002 separated in twomechanical rings corresponding to outer perimeter 1004 and innerperimeter 1014. The base 1002 itself cannot spread the heat from theouter perimeter 1004 to the inner perimeter 1014 thus the two perimetersare substantially thermally isolated from each other. The majority ofthe heat generated in each perimeter ring flows substantially directlythrough the base 1002 backwards into the heat dissipating feature of thefins. By spreading the LEDs 103 into multiple perimeter rings allows fora more even distribution of heat across the front surface of the outerperimeter of base 1002. Within each perimeter ring 1004 1014, the LEDsare substantially distributed uniformly across the circumference of thering, which mean the heat generation along the ring is substantiallyuniform and temperature is substantially uniform, so heat need not bespread along the circumference of the ring. As the heat generated neednot flow laterally, neither radially or along circumference, in base1002, the in plane lateral thermal conductivity of base 1002 is greatlyreduced. This allow for the base 1002 to be made very thin andperforated with openings 1005 1015 for air flow. The openings 1005, 1015and thinnest of the base 1002 has the additional advantage of allowingthe base 1002 to be light weight.

FIGS. 11A-11B depict an isometric view and a front view of an exemplaryheatsink. With reference to FIG. 1B, heatsink 102 includes at least twoheatsink fins 1101, 1102, each fin 1101, 1102 orientated in a radialpattern. At least one of the fins 1101, 1102 is connected thermally andmechanically to either a central column 1103 and, optionally, to a base1104. The connection method may include crimping, riveting, brazing,soldering or gluing. In various embodiments, at least one of the fins1102 may be of a shorter radial length than the other fin 1101. Theshort fin 1102 may be positioned towards an outer perimeter. In such anarrangement, the spacing 1105 between fins 1101 from near the center mayincrease leading to improved airflow and reducing temperature. Anotherbenefit of a shorter fin may be reduced weight.

FIG. 11C depicts an exploded view of an exemplary heatsink. As depicted,the heatsink 102 includes the center column 1103, a plurality of fins1101, 1102 and the base 1104.

FIGS. 11D and 11E depicts an exemplary set of a pair of fins. Asdepicted, fins 1101, 1102 are fabricated from a single piece ofmaterial, such as sheet metal, and folded into shape. The two fins 1101,1102 are connected by a flat base region 1107. The flat base region 1107may be thermally and mechanically attached to the base 1104 or,alternatively, directly to a PCB. If directly attached to a PCB, thepreferred method would be a thermally conductive glue, such as, forexample, an epoxy, silicone, or thermal grease. In various embodiments,the flat base region 1107 may not be continuous but has openings 1108between them. These openings 1108 allow for air to flow when assembledinto the full heatsink 102.

In some embodiments, the flat metal fins of FIG. 9A-11E may have holes.The purpose of this holes allow for air to flow though the fins which isadvantageous if the optical system containing the fins is not mounted ina substantially vertical position. For example, if the optical system isat a skewed angle from vertical or lying horizontal. The holes allow forimproved air flow in such orientations. In some embodiments, the holearea may be at least 20% of the surface area of any particular fin.

Optical Accessory

A secondary optic, or optical accessory, may be placed in front of theprimary optic to redirect at least a portion of a first opticaldistribution into an overall secondary optical distribution. In someembodiments, the primary optical distribution may be modified by theoptical accessory so the overall secondary optical distribution becomesone or more of the following: wider, asymmetrical, provide uplight,reduce glare such as in using louvers, diffuse the light, suitable foraisle lighting.

In various embodiments, the majority of primary light distributionpasses through unaltered by the optical accessory. In some embodiments,between 5% and 75% of the primary distribution may be substantiallyunaltered. In various embodiments, openings, or open regions, in theoptical accessory may pass light through the accessory unaffected.Although such open areas can be filled with a flat parallel window whichdoes not substantially alter the direction of light passing through it,such windows still suffer from Fresnel reflection or a 4% backreflection from each of the two surfaces resulting in an about 8% lossin optical efficiency. Therefore, openings formed from an absence ofmaterial are advantageous as they provide maximum efficiency withoutFresnel losses. Such openings also have the additional benefit ofreduced weight and allowing for airflow.

In some embodiments, the optical accessory may be substantially roundand can be rotated on its center such that any asymmetric secondaryoptical distribution of the accessory rotates with the accessory.

FIGS. 12A-12C depict various views of an exemplary optical accessory.With reference to FIG. 1B, the optical accessory 104 may be used toprovide uplight. The optical accessory 104 includes an optical portion1203 that redirects at least a portion of the primary opticaldistribution. In some embodiments, the optical accessory has an opening1201 that allows for air flow. In various embodiments, the opticalaccessory 104 has mechanical attachment features that allow for mountingto a LED system. For example, the mechanical attachment features mayinclude screws, snaps, or magnets. In an illustrative example, themechanical attachment features enable easy rotation of the opticalaccessory 104 about its center relative to a LED system. As depicted,the optical accessory 104 is attached to the main structure through aseries of snap features 1202. The snap features 1202 are designed insuch a way that allow for easy rotation of the optical accessory 104.The snap features 1202 are designed to snap into a corresponding featurein the primary optic.

FIG. 13A depicts the front view of an exemplary optical system having anoptical accessory. The optical accessory 104 over laps and redirects atleast a portion of the light from the outer ring of optic 323. Theopening 1201 in the optical accessory 104 allows for light from themiddle ring 322 and the inner ring 321 to escape undisturbed. Theopening 1201 further enables air flow to the optic opening 502, the LEDopening 205 and into the interior of the heatsink 102. The opening 1201may also reduce the weight of the optical accessory.

In some embodiments, for the creation of uplight, there is at least oneLED at a periphery near the edge of the mechanics. The mechanics maycomprise the optical system or the heatsink 102. The optical accessorycreates up light by redirecting a least a portion of light emitting fromthe at least one LED at the periphery to create the up light. In variousembodiments, a LED and a corresponding optic may be within 25 mm of anedge of the LED system that does not have the optical accessory.Advantageously, locating the LED near the edge of the mechanics may moreeasily allow for the redirection of at least a portion of light aroundthe mechanics into uplight. In various embodiments, between 5% and 40%of the total light from the LED system is redirected into uplight. Theoptical accessory may have interior opening so that majority of thelight passes through it unaffected.

FIG. 13B depicts a cross section view of an exemplary optical systemhaving an optical accessory. The cross section, at F-F, includes theheatsink base 1305, a PCB 1303, at least one LED package 1302, a primaryoptic and the optical accessory 104. The primary optic includes at leastone optic 1301, an optic holder 1306, and a mating snap feature 1304.

FIG. 13C depicts an illustrative optical ray trace of a cross section ofan exemplary optical system. The LED 1302 is located near the perimeterof the mechanics of the optical system. The mechanics compose an opticalsystem such that a portion of an emitted light may be more easilyredirected by the optical accessory 104 around the mechanics to formuplight 1310. At least one portion of the emitted light from the LED1302 is redirected by the optic 1301 into a first distribution 1315. Atleast a portion of the first optical distribution 1315 is furtherredirected by the optical accessory 104 into an overall secondarydistribution comprising of the unaffected light 1309 and the redirectedlight 1310. In some embodiments, the primary optic 1301 may be in theform of a dielectric CPC with an input surface 1314, a TIR reflectorsurface 1307 and a curved output surface 1308. The optical accessory 104includes an input surface, a first reflector surface 1313, a secondreflector surface 1312 and an exit surface 1316. The input surface andthe exit surface 1316 may share a portion of the same physical surface.The optical accessory 104 has series of snap features 1202 designed tomate to the main optical system via corresponding features in the optic1304. The snap features 1202 may be designed in such a way to allow foreasy rotation of the optical accessory 104 by hand.

FIG. 14 depicts perspective view of an optical accessory. An opticalaccessory, as depicted, may be used to redirect a light into a moreasymmetric profile. The optical accessory having at least two differentregions, a first region 1403 and a second region 1404. Each regionarranged to redirect the light into substantially differentdistributions. The optical accessory further comprising an open region1401 having similar function to the open region 1201. The opticalaccessory includes a snap feature 1402 having similar function to snapfeature 1202.

FIG. 15 depicts a top perspective view of an exemplary optical accessoryhaving an additional optical accessory region 1501 that is used toredirect the light from the interior of corresponding LEDs. Theadditional region 1501 may have an opening region 1502 to allow forimproved air flow into the LED system.

In some embodiments, the optical accessory may be stackable so at leasta portion of light may be redirected by each optical accessory.

Electronic Driver

The LED systems may be powered from at least two types of sources, suchas, for example, directly from offline AC voltage source or from aballast.

In the case of offline operation with AC voltage source 1701, theelectronic LED driver may be powered by AC line voltages including 100VAC to 480 VAC and including frequencies 50 Hz or 60 Hz. Some popularvoltages include 100, 110, 115, 120, 200, 220, 230, 208, 240, 277, 305,380, 400, 415 or 480 VAC. The electronic driver technology for suchoffline supplies include switching mode drivers with various topologies,such as, for example, buck, boost, buck bust, flyback, or combinationsthereof.

In the case of operation with a ballast, such as a magnetic HID ballast,certain challenges need to resolved, for example achieving an acceptablepower factor (PF) and a total harmonic distortion (THD) at the input tothe ballast. Additionally, preventing damage from pulse start ballastswith ignitors that generate approximately 2-5 kV pulses during theinitial warm phase intended for an HID lamp may also need to beresolved. Examples of Pulse start 400 W HID ballast with ignitorsinclude M135, M155, or SD51. An example of Probe start 400 W HID ballastwithout ignitors includes M59.

HID magnetic ballasts are designed for specific HID lamp load. Forexample, a M59 magnetic ballast is designed to power 400 W metal halideHID lamp with good power factor, generally >0.9 or >0.8 and a good THD,generally less than 32% or less than 20%. A LED lamp intended todirectly retrofit to with the same HID ballast would requiresignificantly less power, for example consume 150 W instead of 400 W.This presents a completely different load to ballast and may result in apoor power factor, for example a power factor less than 0.8, and a poorTHD, for example a THD greater than 32%. The LED electronic driver mustoperate to trick the ballast in delivering a significantly lower powerof about 150 W or about 200 W while maintaining a good PF and a good THDto the system.

FIG. 16A depicts a schematic of an exemplary 400 W Probe Start MetalHalide ballast designed to work with a probe start M59 Metal Halide lampload. A ballast 1601 includes a transformer 1606, an output capacitor1605, a series of inputs 1602 and an output 1603. The series of inputs1602 includes multiple taps into the transfer allowing the ballast 1601to operate at different AC voltage sources, such as 277V, 240V, 208V or120V. In an illustrative example, a Metal Halide lamp load 1604 may bereplaced with an electronic driver through a connection 1703. During theinitial operation of a HID lamp, where the HID lamp is in a cold state,the HID lamp has high impedance and the ballast 1601 operating in arelatively constant wattage mode delivers about 300V to the HID lamp. Asthe HID lamp warms up, the impedance drops resulting in a drop involtage to about 130 V.

FIG. 16B depicts a schematic of a 400 W Pulse Start Metal Halide ballastdesigned to work with pulse start M135 Metal Halide lamp load. A ballast1611 includes a transformer 1616, a capacitor 1615, a series of inputs1612 and an output 1614. The series of inputs 1612 includes multipletaps into the transfer allowing the ballast 1611 to operate at differentAC voltage sources, such as 480V, 277V, 240V, 208V or 120V. The MetalHalide lamp load 1614 may be replaced with an electronic driver throughthe connection 1703. The initial high impedance of a HID lamp in a coldstate results in an initial higher voltage across the lamps, forexample, V_(i)>250V. The high voltage may be sensed by ignitor 1620 andcauses it to generate 2-5 kV pulses to help expedite the warm up of HIDlamps. Once a HID lamp warms up, the impedance drops to about 130V. Theignitor senses this drop in voltage and ceases firing.

FIG. 17 depicts a schematic of an exemplary electronic LED driverdesigned to interface with a magnetic ballast. A magnetic ballast 1702(e.g., ballast 1601 or ballast 1611) is powered by an offline AC voltagesource 1701. The ballast 1702 is connected to the electronic LED driver1704 via an electrical connection 1703, for example an E39 or E40 lampbase. The electronic LED driver 1704 includes a capacitor 1708, arectifier bridge 1707, a smoothing capacitor 1708, and optional currentand/or thermal fuses 1705. The electronic LED driver 1704 powers LED1709 with forward voltage V_(f). The input capacitor 1706, disposedbefore the bridge, needs to be bipolar, such as a film type capacitor.The input capacitor 1706 serves as a partial shunt that diverts some ofthe output power and current from ballast 1702 back into the ballast1702 instead of to the LED 1709. The smoothing capacitor 1708 isintended to minimize the current ripple going into the LED 1709. Thepower and LED forward current I_(f), into the LED 1709, is controlled bythe combination of the capacitance in capacitor 1706 and the LED 1709forward voltage, V_(f). A M59 ballast, with an input capacitor 1706 ofabout 22 uF and a LED with forward voltage of about 140V, will result inapproximately 150 W delivered to the LED 1709. The value of thesmoothing capacitor may be set to 1000s uF. In such a configuration, atthe input to the ballast 1702, the PF is about 0.89 with a relativelyhigh THD, at 48%.

In some embodiments, the input capacitor 1706 may be reduced to 10 uFand the LED 1709 forward voltage V_(f) may be reduced to between65V-75V. This results in an improved power factor of 0.92 and asignificantly improved THD of 23% with power, about 200 W, delivered tothe LED 1709. The load voltage experienced by the ballast output issubstantially equal to the LED forward voltage, which is well below thevoltage needed for the ignitor to fire Voltage V_(i) of about 250V.Thus, in such an arrangement, the electronics driver components areprotected from the ignitor high voltage pulses.

The LED 1709 has a forward Voltage V_(f) and a LED current I_(f). TheLED 1709 may be the previously referenced LED 101 that is part of theoverall LED system 100.

FIG. 18 depicts a schematic of an electronic LED driver designed tointerface with a magnetic ballast. The electronic LED Driver having abridge, a switch controlled by a controller unit, a smoothing capacitorand a string of LEDs with total forward voltage V_(f). With reference toFIG. 17, FIG. 18 consists of the addition of a switch 1802 controlled bya controller unit 1803. The switch 1802 may be a MOSFET, or any otherdevice or combination of devices that have relatively low impedance whenactivated and have a current carrying capacity for at least a portion oftime to shunt the power and current back into the ballast 1702. Theswitch 1802 may be designed to selectively shunt a portion of the powerand current from the ballast 1702 back to ballast 1702 therebyregulating the power into the string of LEDs 1709. The controller unit1803 may have selective sensor inputs. The selective sensor inputs mayinclude a LED current from current sensor 1805, the output voltage V_(B)from rectifier bridge 1707, a voltage across capacitor 1708, atemperature of the string of LEDs 1709 or a temperature of theelectronic LED driver 1801 itself. The controller unit 1803 senses theseinputs and controls the switch 1802 accordingly to regulate the LEDforward current I_(f). The controller unit 1803 may simply be aselection of discrete components or more flexibly be a microprocessor ormicro controller unit. If the controller unit 1803 is able to sense thephase of the input voltage, such as, for example, by monitoring thevoltage V_(B) across the bridge 1707, switching can be in phase orsynchronous with the line frequency. In some embodiments, the controllerunit 1803 may control the switch 1802 regardless of phase or inheuristic control manner that is asynchronous with the input voltagewaveform.

The main purpose of the controller unit 1803 is to the control switch1802 in a manner that regulates the LED current to some predeterminedmanner. One advantage of FIG. 18 over FIG. 17 is that the controller1803 can regulate current I_(f) to the LED 1709 more precisely toaccommodate variations in the line voltage V_(s). For example, V_(s)commonly varies at ≧10% and the controller unit 1803 can sense the LEDcurrent I_(f) and adjust the switch 1802 to maintain a substantiallypredetermined current level. Further, when the temperature of the systemexceeds some predetermined value, either for safety or to prolonging thelife of the system, the controller unit 1803 can reduce the current tothe LED 1709 thereby reducing the heat generated regulate the overtemperature, a feature known as thermal roll back. Another advantage ofthe controller unit 1803 may be configured to dim the system when lesslight is required.

In reference to FIG. 18, and assuming a constant supply voltage V_(s),the ballast 1702 may supply substantially a constant ballast currentI_(Ballast) over a range of Ballast loads. Table 4 summarizes themaximum power delivered to the LED (I_(f)·V_(f)), using the schematic ofFIG. 18, where ballast 1702 is a M59 HID ballast and switch 1802 is inan open state. By leaving switch 1802 in an open or deactivated, none ofthe current from the ballast is shorted back to itself, instead all thecurrent is sourced to LED (I_(f)=I_(Ballast)) which allows thedetermination maximum possible delivered power to the LED. In Table 4,the current I_(f) is substantially constant with changing LED forwardvoltage V_(f) resulting in the power delivered to the LED to besubstantially proportional to the LED forward voltage V_(f). If there isno variation in ballast input voltage V_(s) and no variation in thecomponents such as the ballast or LEDs, the system power can simply bemaintained by setting the LED forward voltage and there is no need forincorporation of switch 1802 or controller 1803. In reality, the ACsource voltage can vary by at least +/−10% which leads to a ballastcurrent to vary approximately proportionally or I_(Ballast)αV_(s). Also,the ballast may vary from unit to unit and with aging which also affectsthe ballast current I_(Ballast). The addition of switch 1803, and 1802compensates for such variations. The activation of switch 1803 can onlydecrease the delivered LED power from the maximum possible deliveredpower, so it is necessary to set the LED forward voltage V_(f) such thatthe maximum possible deliver power is higher than the nominal power. Inthe nominal situation, the switch activates with the required duty cycleto reduce the delivered power to the desired nominal level. For example,in the case of Table 4, assume the nominal desired power is 175 W andassume the ballast current can vary I_(Ballast)=2.6 A+/−15%. The systemwould be designed such the maximum possible power level at the nominalballast current would be at least 15% greater than 175 W or about 201 W.This would correspond to a minimum required LED forward voltage of aboutV_(f)≧79.8V. To deliver only 175 W at V_(f)=79.8V, the LED forwardcurrent need to be regulated to about 2.19 A instead of 2.6 A (175W=79.8V·2.19 A). This may be accomplished by controller 1803 monitoringthe LED forward current I_(F), using current sensor 1805, and producingan appropriate duty cycle in switch 1802 such that average LED forwardcurrent is controlled to about I_(f)=2.19 A, with the excess currentbypassed by the switch back to the ballast. In such a scenario, theswitch is always switching under nominal conditions with an appropriateduty cycle to maintain a LED forward current I_(f) less than the ballastcurrent I_(Ballast) i.e. I_(Ballast) (2.6 A)>I_(f) (2.19 A). However, ifI_(Ballast) fluctuates away from it nominal current of I_(Ballast)=2.6 Ato I_(Ballast)<2.19 A, the switch can no longer regulate the LED currentto I_(F)=2.19 A, as at most can LED current I_(F) only be equal theballast current to I_(B). Thus, to be able to maintain regulation aroundthe nominal condition, at the nominal operating point, the LED forwardcurrent I_(f) must always less than the ballast current I_(Ballast)(I_(f)<I_(Ballast)), and switch 1802 is always switching to maintainthis condition. In some embodiments at nominal operation conditions theLED current satisfy I_(f)<0.95 I_(Ballast) or I_(f)<0.9 I_(Ballast) orI_(f)<0.85 I_(Ballast)

There are least four possible advantages of having the switch 1802 andcontroller 1803:

-   -   a. Maintains LED current to a predetermined level even there is        a fault or variations in the system, including if the wrong        ballast is used to power the LED electronic driver.    -   b. With an addition of a temperature, the switch can be used to        reduce the LED current to maintain a predetermine temperature.        This is especially important for example in a fault condition        the abnormally raises the system temperature.    -   c. The switch can reduce current for dimming of the LED output.    -   d. The switch allows for a less stringent specification of the        LED voltage as long as the LED voltage is above a minimum        required value.

TABLE 4 LED Forward Ballast Maximum Possible Voltage Current Power toLEDs V_(f) I_(Ballast) I_(Ballast) · V_(f) (Volts) (Amps) (Watts) 59.12.66 157 61.8 2.61 161 64.8 2.60 168 67.7 2.58 175 70.7 2.55 180 73.62.55 188 76.7 2.53 194 79.8 2.53 202

In some embodiments, the controller unit 1803 also regulates the LEDcurrent while improving the PF and/or THD at the input to the ballast.

In various embodiments, the system consists of a HID ballast, anelectronic driver, and a LED string. The HID ballast may have a set ofinputs powered by an AC voltage source and a set of outputs to power theelectronic driver. The ballast sourcing a ballast current I_(Ballast) atits output. The electronic driver having at least a rectifier and aswitch. The rectifier inputs are connected to the ballast output and therectifier output is connected to the LED string. The switch beingconnected in parallel across the bridge output and across the LED stringsuch when the switch is deactivated, the ballast current I_(Ballast),substantially flows to the LED string and when the switch is activated,the switch substantially shorts the LED so the ballast currentI_(Ballast) is diverted through the switch back the ballast thusbypassing LED string. The switch is switched in a pattern to maintain adesired forward current I_(f) into the LED. The LED forward voltage isset to a minimum value, such that under nominal conditions the averageballast current is always less than the LED forward current,I_(f)>I_(Ballast). In some embodiments, there may also be a temperaturesensor and the switch is switched in a pattern to reduce the currentinto the LED and to maintain a predetermined temperature set point. Infurther embodiment, there may be a capacitor across the LED to smoothout the current ripple and a diode before the capacitor to block thecapacitor current flowing back to the switch.

FIG. 19 depicts possible methods by which a controller unit controls aswitch. A scheme 1910 shows the equivalent rectified offline voltagesource 1701 or V_(s). Note the rectified bridge voltage V_(B), will havesame periodicity as the scheme 1910 but may of a different,non-sinusoidal shape due to distortion from a ballast. Nevertheless, thebridge voltage V_(B) may be used to sense the periodicity of the offlinevoltage V_(s) which may be of a fixed phase offset. Schemes 1920-1970show possible schemes to control the switch 1910 relative in timing tothe phase of rectified voltage 1910 to regulate the LED current withpossible benefit to improve PF and/or THD at the input to the ballast.

In scheme 1920 and 1930, the switch 1802 is controlled in phase or witha fixed phase offset with rectified voltage V_(B) 1910, and there is asingle on/off cycle within each cycle of the rectified voltage V_(B)1910. As such, the frequency of the scheme 1920 is the same as thescheme 1910 which is twice the line voltage frequency Vs 1701. Thescheme 1920 is symmetrical within the cycle whereas a scheme 1930 isintended to represent a class of schemes where the pulse of an arbitraryshape need not be symmetrical within the cycle. By intentionallyoffsetting the pulse from the peak of the voltage, the load can crudelybe made to seem to be inductive or capacitive thus such pulse pattern isintended to improve PF or THD at the input to the ballast. The pulsepattern may also be used to simulate a nonlinear load to generateharmonics to cancel out harmonics in the ballast to overall improve THD.In some embodiments, the equivalent impedance, whether linear ornonlinear may vary within the duty cycle. Such control scheme is laterdescribed with reference to FIGS. 23-25.

In scheme 1940, the switch 1802 is controlled in phase or with a fixedphase offset with rectified voltage V_(B), but there is not a fullon/off cycle of the switch 1802 within each cycle of the rectifiedvoltage V_(B), thus the frequency of the scheme 1940 is lower than thescheme 1910.

In scheme 1950, the switch 1802 is controlled in phase or with a fixedphase offset with rectified voltage V_(B), but there is more than asingle on/off cycle of the switch 1802 within each cycle of therectified voltage V_(B). Thus, the frequency of 1940 is higher than1910. In some embodiments, the frequency may be 2×, 4×, 10×, 100×,1000×, 10,000× that of the rectified line frequency or alternative >10KHz. One advantage of a higher frequency system is it more regularlycharges the capacitor 1708 thus reducing the required capacitance. Invarious embodiments, the switching frequency may be equal or great than2× the rectified line frequency but still of a sufficiency lowfrequency, for example less than <10× rectified line frequency, suchthat the inductance the output of the ballast does not impede theshutting of current back to the ballast. For example, a typicalinductance of the output winding of a M59 ballast is about 1000 mH. Inother words, the ballast output may have sufficient inductance that ifthe switch 1802 is operated at too high a frequency, it may noteffectively shunt the current and power from the ballast back into theballast.

In scheme 1960, the switch 1802 is controlled out of phase withrectified voltage V_(B). This scheme 1960 may more broadly encompass theswitch patterns and frequency of the 1920-1950 but out of phase withrectified voltage V_(B) of the scheme 1910. Such a class of asynchronouscontrol include heuristic control, for example only switching asnecessary to keep the voltage or current controlled to somepredetermined range. Such a control scheme 1960 is simpler in that thecomplexity of sensing the phase, then syncing to the phase of the inputvoltage is not needed.

In scheme 1970, the switch 1802 controlled in phase with rectifiedvoltage V_(B) of the scheme 1910, but the switching pattern is intendedto be arbitrary within each period but repetitive in each subsequentperiod. For example, in the specific scheme 1970, the frequency ishigher at the beginning of the cycle and changed smoothly to a lowerfrequency. Such a scheme will more precisely simulate capacitive orinductive needed to improve PF and THD at the input to the ballast.

FIGS. 20A-20F and 21A-21D depict various schematic of an exemplarysingle LED driver specifically designed to be able to be power by eithera magnetic ballast or directly with the offline AC source V_(s). Such animplementation has the advantage in that a single product can addressboth types of power sources. However, this increases complexity as thedriver must resolve one or more of the following issues:

-   -   a. Achieve acceptable PF and low THD for both types of power        sources. Acceptable PF for example may be >0.7, >0.8 or >0.9.        Acceptable THD for example may be <50%, <32%, <20%.    -   b. Prevent damage from a ballast containing ignitors that may        fire high voltage pulses.    -   c. Sense the type of power source to configure both in hardware        or software the type of control schemes to accomplish #1 or #2        above.

In FIGS. 20A-20F and 21A-21D, a set of dotted lines is used to indicatewhen the AC offline voltage source 1701 is connected to the driver inputconnection 1703 and a set of solid lines are used to indicate when theballast 1702 is connected to the driver input connection 1703. Note, itis not intension to connect both the AC Offline voltage source 1701 andthe ballast 1702 simultaneously to the driver 2001 input connection1703.

In FIG. 20A, the electronic driver 2001 has a switch 2002 that issimilar to prior switch 1802, and a controller 2003 that is similar toprior controller 1803 and includes all the control and switching schemes1920-1970, but this time rather than regulating the current I_(f) in theLED 2009, the combination of controller 2003 and switch 2002 may bedesigned to regulate either the voltage or current entering regulator2010. The regulator 2010 may then be used to regulate the current I_(f)to LED 2009. A diode 2011 is prevents current from the regulator 2010flowing backwards through switch 2002. The regulator 2010, for example,can be a switching mode regulator, such as, for example, a buck, boost,buck boost, fly back or combination therefore including multipleswitching stages. Alternatively, the current regulator 2010 can be alinear regulator. An optional current sensor 2016 may measure thecurrent going through the switch 2002.

FIG. 20B shows a possible embodiment of FIG. 20A where the regulator2010 consists of a first stage including a diode 2011, a capacitor 2008and a second stage regulator 2011. The regulator 2011 has regulatedvoltage V_(SC) at its input. Controller 2003 regulates voltage V_(SC).By using a two-stage method of 20B, the voltage regulation of V_(SC)need not be very tight. For example, if the regulator 2011 is a buckboost current regulator, the input V_(SC) may vary, for example, eitherhigher or lower than the LED forward voltage V_(f).

In an embodiment for FIG. 20B, the maximum regulated voltage at V_(B)should always be less than the ignitor trigger voltage V_(i), by doingso, the ignitor may be prevented from firing its high voltage pulses.For example, if the controller 2003 senses the bridge output voltageV_(B) is approaching ignitor trigger voltage V_(i), then the switch 2002may be activated to short, for at least a portion of time, in a mannerto ensure the V_(B)<V_(i). During the portion of time the switch 2113 isactivated, the switch 2113 substantially shorts the bridge outputvoltage V_(B) to be near 0V which is less than the ignitor triggervoltage.

In some embodiments, the current regulator 2011 is a buck regulator. Thevoltage V_(sc) across the capacitor 2008 is substantially regulated bythe controller 2003 and switch 2002 to be higher than the LED 2009forward voltage V_(f) but less then ignitor trigger voltage V_(i)preventing the ignitor from firing.

In another embodiment of FIG. 20B, the capacitor 2008 is designed tohave the necessary capacitance to absorb a sufficient amount of energyfrom the ignitor pulse to bring down the peak pulse voltage to anacceptable level that do not damage the driver components which isgenerally below the voltage rating of the components. As an example, wecan calculate the necessary capacitance C₂₀₀₈ to sufficiently absorb thepulse energy from a M59 ballast ignitor by using the followingparameters about the ballast: M59 output winding inductance is aboutH_(B)=1 Henry or 1H, M59 output short circuit current is about I_(SC)=4A, the maximum voltage at the ballast output is about V_(Z) _(_)_(M)=250V, and the voltage rating of the capacitor 2008 is aboutV_(R)=450V. Then the necessary capacitance C₂₀₀₈ is given by thefollowing formula:

$C_{2008} \geq \frac{I_{SC}^{2} \cdot H_{B}}{\left( {V_{R} - V_{Z\_ M}} \right)^{2}} \geq \frac{4^{2} \cdot 1}{\left( {450 - 250} \right)^{2}} \geq {256\; {uF}}$

Note the voltage rating of the capacitor 2008 also needs to also besufficient to accommodate the worst case offline voltage. For example,if offline voltage source has a nominal RMS voltage V_(s)=277 VAC with amaximum 10% over voltage then the voltage rating of the capacitor V_(R)needs to higher than the peak of this AC line under worse or:

V _(R)≧277·1.1·√{square root over (2)}≧431V

Therefore, a capacitor with a voltage rating of 450V will be suitablefor being powered by both an offline voltage source Vs=277V and by a M59ballast.

In other scenarios, the capacitor 2008 has a capacitance C₂₀₀₈≧100 uF,≧200 uF or ≧500 uF with a voltage rating V_(R)≧200V, ≧450V or ≧750V.Such large capacitance values are generally much larger than typicallypresent in EMI filters with capacitance on the order of <10 uF or <1 uF.

One advantage of correctly sizing the capacitor 2008 with sufficientcapacitance is it will be able to continuously sustain ignitor pulses,for example in circumstance where controller 2003 or the currentregulator 2012 cannot guarantee V_(B)<V_(i). Such circumstances mayinclude, if the control circuit is missing, malfunctions, disabled orthere is noise, surges in the power line.

In various embodiments, the controller 2003 may be designed to activatethe switch 2010 if the rectified bridge 1707 voltage V_(B) is sensed tobe approaching or be above a certain level limit voltage V_(c), such as,for example, V_(c)>200V, V_(c)>250V, V_(c)>300V. It is desirable thelimit voltage V_(c) is less than the ignitor trigger voltage V_(i) tosuppress the ignitor in the ballast from firing. The switch 2002 staysin an activated shunt position until such a time it will not cause theballast output voltage to rise above the ignitor trigger voltage, V_(i).For example, an energy storage unit in the regulator 2010, such as thecapacitor 2011, may sufficiently drain to a level where the opening ofthe switch 2008 will cause the charging of the energy storage unit. Insuch a condition, the charging of the storage unit will result in arelative low impedance in the regulator 2010 resulting in a lowervoltage V_(B) that should be below the ignitor trigger voltage orV_(B)<V_(i).

One key issue may be the switch 1705 of FIGS. 20A-20B needs to bedeactivated (off) or in a high impedance mode, when the driver 2001 isdirectly connected to the offline voltage source 1701, otherwise it willshort circuit the line voltage and cause the fuse or other components1705 to exceed their current rating. This can be prevented if thecontroller 2003 can sense if the driver is connected to ballast 1702 ordirectly connected to offline voltage source 1701. In some embodiments,this sensing is accomplished by monitoring the current I_(s), usingcurrent sensor 2010. The short circuit current I_(s) will besignificantly higher when connected to offline voltage source 1701,I_(s)(offline), than when connected to Ballast, I_(s)(ballast). In otherwords, I_(s)(offline)>>I_(s)(ballast). For example, the short circuitballast current I_(s)(ballast) for a M59 ballast I_(SC)(ballast)≈4 A RMSor 7 A Peak, whereas, assuming Vs=120 VAC and a switch resistance of 5ohms, the short circuit current of the offline voltage sourceI_(s)(offline)≈24 A RMS or 32 A peak which is significantly higher thanI_(SC)(ballast)≈4 A. The sensing should occur within a relatively shorttime period, for example <0.25 seconds, <0.5 seconds, <1 second, or <2seconds during the initial power up of the driver to prevent thepotential of a short circuit current in switch 2002 from damaging thedriver in the case it is connected to offline voltage source 170.

When the electronic driver of FIG. 20B is operated directly from theoffline voltage source 1701, the switch 2002 is deactivated and thesystem is essentially a regulator 2012 with a large capacitor on thefront. Generally, such a capacitor on the input side of the driverresults in poor PF and poor THD performance. In a further improvement,as depicted in FIG. 20C, the capacitor 2008 has a series switch 2026.The switch 2026 is controlled such that when powered from a ballast1702, the switch 2016 switches the capacitor in parallel with theregulator 2012. When powered directly from an offline power 1701, theswitch 2016 switches out the capacitor to improve PF and THDperformance.

In an alternative embodiment to improve PF and THD, as shown in FIG.20D, the capacitor 2008 of FIG. 20B is replaced with a Valley Fillcapacitor arraignment consisting of capacitors 2014, 2013 and diodes2015. The advantage of such a system, the switch 2016 may not berequired thus reducing complexity. Another advantage may be that totalvoltage rating for the capacitor 2018 is reduced and split betweencapacitor 2014 (V_(C2)) and 2013 (V_(C1)) so each individual capacitorcan be of a lower rating. However, the individual capacitance values ofthe capacitors 2013, 2014 needs to increase such that their combinationin series is similar to total required capacitance of the capacitor2008.

In an alternative embodiment, as shown in FIG. 20E, the switchingassociated components 2002, 2003, 2010 are intentionally removed suchthat the system is a regulator 2012 with a valley fill circuit frontend. The advantage of such a system may be reduced complexity as noswitching (outside of regulator 2012) may be needed and the system doesnot need to sense if it is powered by a ballast or powered directly tooffline voltage source. The disadvantage may be without the switch 2002to shunt the power, the PF and THD of the system will likely suffer.

FIG. 20F shows an improvement to 20E, where the capacitor 2017 is placedin front of bridge. The benefits of the capacitor 2017 include improvedTHD, PF when operating with a ballast, and a reduced peak from theballast. The capacitor 2017 is similar in specification and performs thesame function as already described for the capacitor 1706. For example,the capacitor 2017 needs to be bipolar, such as a film type capacitor,and serves as a partial shunt that diverts some of the output power andcurrent from the ballast 1702 back into the ballast 1702 instead of tothe components after the bridge.

The valley fill circuitry shown in FIGS. 20D-20F, and elsewherereferenced, in this document can be modified further to improve THD andPF by using the modifications shown in FIGS. 20G-20H. A resistor 2018may be added to the Valley Fill Circuitry. FIG. 20H shows a furtherimprovement of a version of a Valley Fill Circuitry where two additionalcapacitors 2019-2020 are added with a center tap 2021 that is connectedto the input side of the bridge. The capacitors 2019-2020 may maintaincurrent flow during a longer portion of the voltage cross over andthereby improve PF and THD. To fill in the cross over point requiresonly a very small amount of power so the capacitance value of thecapacitors 2019-2020 may be of a magnitude smaller than the capacitors2013-2014. A resistor 2022 in series with the capacitor 2013 may beadded to reduce current spike. Such a circuit may be capable of PF>0.9and THD<20%.

The function of the Valley Fill circuitry, previously described, to becapable of at least one or more of the following functions:

-   -   a. Sized with sufficient capacitance and voltage rating to        absorb the pulses from an ignitor when operated from a ballast,        such as ballast 1702.    -   b. Sized with sufficient capacitance to smooth out the voltage        V_(SC) to the current regulator 2012.    -   c. Improve PF and THD operation when operated directly from an        offline AC voltage source 1701.

The following summarizes the embodiments of FIGS. 20A-20H. A LED driverthat may be powered by least two different external power sources, thefirst power source being a ballast and the second power source being anAC voltage source. The LED driver including a bridge rectifier, theinput of the bridge connected to the external power source, the outputof the bridge connected in parallel to a switch, and also in parallelwith a regulator. A regulator may be designed to regulate the current toone or more LEDs.

In some embodiments, the sensing the presence of either the ballast orthe AC voltage source occurs with a predetermined length of time afterthe power up of the system. A sensor detects the presence of either theballast or the AC voltage source. The sensing occurs during the power upof the system. The switch may be deactivated or in a high impedance modewhen AC voltage source is detected. If a ballast is detected, the switchperiodically activates according a predetermined scheme to regulate thecurrent or the voltage going into the current regulator.

In various embodiments, at least one equivalent capacitor may beconnected in parallel with the bridge output. The capacitor may be ofsufficient capacitance to absorb the pulses from an ignitor such thatthe resulting pulse voltage is reduced <500V. The equivalent capacitormay be arranged in a Valley Fill circuit arrangement. In someembodiments, the switch and its associated circuitry may be removed.

The driver 2001 of FIGS. 20A-20H may include further elements, notshown, such as EMI filters, PF correction or THD correction circuitry.For example, a simple EMI filter includes a PI filter having 2capacitors arranged in parallel to bridge output with either one or bothsides of the capacitor connected by one or more inductors. The EMIfilter can be placed before and after the bridge rectifier.

FIGS. 21A-21D depict various schematics of an exemplary electronic LEDdriver designed to be powered by a ballast or to be powered directlywith the offline AC source. In the prior implementations of FIGS.20A-20D, the switch 2002 may be designed to deactivate or be in a highimpedance when connected directly to the offline AC source 1701 so thatthe regulation of the LED current I_(f) is taken over by currentregulator 2010, whereas in FIGS. 21A-21D, the switch 2112 in combinationwith the controller 2113 is implemented to regulate the LED current whenpowered by ballast 1702 or powered directly by the offline AC source1701. As such, the switch 2112 may not be deactivated when powered tooffline AC source 1701.

FIG. 21A depicts the LED driver 2101 having a switch mode regulator2115, the bridge 1707, optional temperature and/or the current fuse1705, a EMI filter 2114. The EMI filter 2114 can be placed after thebridge as shown or before the bridge, or both. The switch mode regulator2115 regulates the forward current, I_(f) to LED 1709. The switch moderegulator 2115 includes at least one equivalent inductor 2114 and aswitch 2112 controlled by controller 2113. The switch 2112 and theinductor 2114 are connected in such a method that, at low frequency(e.g., DC to 240 Hz), will substantially shunt or short current from theone side of the bridge back to the return side of the bridge. This isnecessary in the case of being powered by a ballast and is an example ofswitching mode topologies (e.g., Boost, Buck-Boost, SEPIC, CUK, Flyback,Forward, Push-Pull, half bridge, resonant LLC) that will shunt theoutput of the bridge at low frequencies. However, a boost topology willnot accomplish this. The combination of the inductor 2114, the switch2112 and the controller 2113 substantially regulate the current I_(f) tothe LED 1709. In some embodiments, there may be at least two distinctschemes to control the switch 2112. A first scheme when powered with aballast 1702 and a second when directly power with the offline AC source170. In various embodiments, there may be a third switching schemeduring initial power up of the system. The third switch scheme may beused to achieve at least two functions: The first function may be todetect if the power source may be the ballast 1702 or an offline ACvoltage source 1701, and the second function may be to ensure there isnot an over current short circuit situation when hooked to the offlineAC voltage source 1701 or alternatively an overvoltage situation whenpowered by ballast 1702. For example, when the system powers up, thesystem connects to an offline AC voltage source 1701 and switches at arelatively high frequency, for example a switch scheme with substantialfrequency content >10 KHz where the inductor 2114 at the frequencycontent is specified at a value that has non-negligible impedance andserved to limit the maximum current. As such, a short circuit currentmay be prevented, as would be the case with a low frequency switchingscheme that would short circuit and damage the system. However, if thedetected current, either through the switch 2112 or the controller 2113,is not as would be expected from an offline AC voltage source 1701 thenthe controller will change the switching scheme to that used for aballast, such as, for example, a switching scheme with substantialfrequency content <10 KHz or <1 KHz or <240 Hz. The lower frequency maybe necessary as the ballast output winding will have an impedance valuesignificantly higher than the inductor 2114, for example >10×. As such,the inductor 2114 becomes negligible and the switching frequency contentnecessary to function with the ballast may be substantially lower, forexample, 10× lower than the case with the offline voltage source 1701.The switching scheme both for high and low frequency include thosealready described in FIG. 19, such as those intended to improve PF andTHD.

The EMI filter 2114 includes at least one of the following twofunctions: a first function of filtering out EMI and EMC noise from aregulator and a second function absorbing the pulses from the ignitor inthe ballast such the resulting pulse are at an acceptable value. Aportion of the EMI filter may compose of a Valley Fill circuitry.

In FIG. 21B, the regulator 2115 is configured in the form similar to aboost converter where the inductor 2114 is connected before the switch2112. When the controller 2113 senses the electronic driver is directlypowered by an offline AC source 1701, it switches the switch 2112 to ahigh frequency as would be expected in a switching mode power supply,for example >10 kHz. The entire unit performs as a boost converter wherethe inductor 2114 has non-negligible impedance. However, when thecontroller 2113 senses it is connected to the ballast 1703, thecontroller 2113 switches at a much lower frequency, for example <10 KHz,<1 KHz, <240 Hz or for example, at 120 Hz. At this lower frequency, theinductor 2114 is of substantially negligible impedance and the systemsustainably operates the same as depicted in FIG. 18. When operating ina boost converter mode the LED voltage must always be higher than thepeak voltage of input offline AC source 1701. In the event where theoffline voltage source 1701 is Vs=277 VAC, the peak voltage is 391V sothe LED string must be greater than the voltage which would require manyLEDs to be string together. Another issue may be the higher voltage hasmore stringent component and safety requirement.

FIG. 21C shows an improvement to FIG. 21B where diode 2120 is added toconnect the output of the bridge 1707 to the capacitor 2108 so that inthe event that a pulse is generated by the ballast 1702, the diode 2111conducts this energy to the capacitor 2108 to at least partially absorbthe energy to an acceptable level. The calculation for the necessarycapacitance for the capacitor 2108 is the same as previously describedwith reference to FIG. 20B. One advantage of this arrangement may bethat the capacitor 2108 is after the switch 2112 and the inductor 2114,rather than directly at the input as in case of FIGS. 20B-20F, and theswitch 2112 in combination with the inductor 2114 can be configured toswitch in such a manner to optimize for PF.

FIG. 21D shows the implementation of the regulator 2115 in the form of aSEPIC with addition of the capacitor 2117 and the inductor 2118. FIG.21E shows the implementation of the regulator 2115 in the form of a CUKconverter with addition of the capacitor 2117, the inductor 2119, andthe diode 2111 removed and replaced with diode 2120 in a new position.

In FIG. 22, the electronic driver 2101 is configured in the form similarto a flyback converter with the addition of the transformer 2214. Theswitch 2112 is connected in series with the input winding of thetransformer 2214 and connects the transformer output winding to returnor ground. The transformer input winding serves a dual function as theinductor 2114 as described previously. When the controller 2113 sensesthe electronic driver 2101 is directly connected with the offline ACsource 1701, it switches the switch 2212 at higher frequency as would beexpected in a switching mode power supply, for example >10 kHz. Theentire unit performs as flyback converter where the transformer 2214 hasnon-negligible impedance. However, when the controller 2113 senses tothe ballast 1703, the controller 2113 switches at a much lowerfrequency, for example <10 KHz, <1 KHz, <240 Hz or, for example, at 120Hz. At this lower frequency, the inductor 2114 may be of a substantiallynegligible impedance and the system sustainably operates the same asFIG. 18.

In a further embodiment to FIGS. 21A-21E, when connected to a ballast,the controller 2113 controls the switch 2112 in a combination of atleast two substantially different frequency content, a higher frequencycomponent 2330, 2332 and a lower frequency component 2331. The lowerfrequency component 2331 may be sufficient to shunt a portion of thepower and current from the ballast back into the ballast therebybypassing the LED. The lower frequency component 2331, for example, <10KHz, <1 KHz or at 120 Hz, being at the such a lower frequency than theimpedance of the inductor 2114, or the equivalent inductor of the firstwinding of the transformer 2214, may be negligible. The higher frequencycomponent 2330, 2332 is sufficient to effectively transfer power to theLED through the transformer 2214 or the inductor 2114. The higherfrequency for example may be >10 kHz. In some embodiments, thecontroller 2113 ensures the output voltage of the ballast 1703 or thatthe bridge voltage V_(B) is always below the voltage that triggers theignitor in the ballast, for example, <200V, <250V, <300V.

The trace 2320, as depicted in FIG. 23, shows the equivalent rectifiedoffline voltage source 1701 V_(s) or the rectified ballast outputvoltage V_(z). Note the rectified bridge voltage V_(B), will have thesame periodicity the line voltage V_(s), but may be of a different andnon-sinusoidal shape due to distortion from ballast. Nevertheless, thebridge voltage V_(B) may be used to sense the periodicity of the offlinevoltage V_(s). The schemes 2321-2322 are examples of how the controller2113 may be used to control the switch 2112 in the presence of a ballast1702. Both schemes 2321-2322 have at least two distant frequencycomponents, a lower frequency component 2231 intended to shunt the powerand current from the ballast, and a higher frequency component 2231intended to transfer power across the transformer 2214 or the inductor2114.

FIG. 22 depicts a preferred implementation of an electronic driver thatis both compatible with an offline voltage source 1701 and with aballast 1702. A fly back topology provides isolation and a flexible LEDforward voltage may not be dependent on the source voltage at the inputto the driver.

The following summarizes the illustrations depicted in FIGS. 21A-21E andFIGS. 22-23. A LED driver that can be powered by least two differentexternal power sources, a first external power source being a ballastand a second power source being an AC voltage source. The LED driverincludes a bridge rectifier, the input of the bridge connected to theexternal power source, the output of the bridge connected switch inseries with an inductor. A sensing mechanism that detects the presenceof either the ballast or the AC voltage source. The sensing occursduring the power up of the system. A switch may be activated by at leasttwo different switching patterns, a first switching pattern when poweredby a ballast and a second switching pattern when powered by an ACvoltage source. The switch activation pattern shorts the inductor to thebridge return and may be designed to regulate the current into the LEDfor both power sources. The first switching pattern to have a lowerfrequency content than content than the second switching pattern.

FIG. 24A depicts a control arrangement for an LED driver 2421 thatincorporates power factor correction. The power conversion circuit 2420is constructed such that its input current is forced to be substantiallyproportional to the signal V_(c). In this case the signal V_(c) iscreated by the multiplication between the rectified voltage V_(B) andthe error signal V_(Error) or V_(c)=(V_(B)·V_(Error)) orI_(in)α(V_(B)·V_(Error)). The equivalent resistance R_(D) the driverpresents to the AC source 1701 is R_(D) a R_(D)αV_(B)/I_(in) whichsimplifies to R_(D)α1/V_(Error). The V_(Error) signal can be kept to arelatively constant average value by filtering its frequency contentwith a low pass filter 2411 such that it changes at a rate that is muchlower than the AC input frequency (bandwidth of the filter 2411<60 Hz/10for example). If V_(Error) is kept relatively constant, then theequivalent resistance R_(D) will also be relatively constant. The outputcurrent feedback 2116 adjusts the V_(Error) Signal to keep the LEDstring current I_(f) at a constant value as set by the LED current setpoint 2410 or V_(IS). Some other components in the system include 2414 asensor detect the rectified line voltage, a multiplier 2412, an inputcurrent sensor 2405 and a LED current sensor 2105. The power conversioncircuit may have energy storage components such capacitors that is usedto store input current for a portion of the AC line voltage cycle, thenlater releasing the stored energy to the LED in another portion of theAC line voltage cycle. The power conversion circuit may be capable topresent very high impedances similar to an open circuit or very lowimpedance such a short circuit.

In FIG. 24B the inclusion of a waveform generator 2413 is used affectthe signal V_(c). In such an arrangement, the control arrangementbecomes capable of presenting real and reactive and non-linearimpedances to at the electronic driver 2431 input 1703. For example, theinput current may be shifted in phase with respect to the input voltageV_(B), making the driver appear as a parallel combination of capacitanceor inductance and resistance to the ballast. The waveform generator canalso generate harmonics of the power line frequency resulting in anonlinear load. This allows the input current to be any wave shape bysumming the correct harmonics components. This may be advantageous whenthe electronic driver 2431 is connected to a ballast as the ability topresent an inductive, capacitor or nonlinear to load may be used toimprove power factor or THD at the input to the ballast. To furtherimprove PF and THD, the impedance, linear and/or nonlinear need not beconstant but change within a half cycle of the line frequency. Thehigher harmonic nonlinear load presented to the ballast may be necessaryto cancel out the harmonic distortion created by the ballast which maynot be possible purely linear reactive, capacitive or resistiveimpedances.

The control scheme described for driver 2431 may be implemented usingtopologies similar to electronic driver 2001 or 2101 where the powerconversion circuit composes of at least a switch similar in function asswitch 2002 or 2112 and where the waveform generator 2413 may result inpower conversion circuit 2420 to switch with waveforms similar to FIG.19.

The optimal current wave shape or non-linear impedance to optimize theinput power factor and distortion of the ballast may be set by thewaveform generator. If the waveform generator is configured to providethe input voltage or a scalar multiple of the input voltage to themultiplier the control arrangement of FIG. 24B, it then may becomefunctionally equivalent to the control arrangement of FIG. 24A. Thisarrangement can therefore be configured to operate from a ballast ordirectly from the AC line.

FIG. 25 shows a process for selecting the operational mode of the driverand for configuring the control circuit for optimal ballast input powerfactor and harmonic distortion for multiple ballast types. When thedriver first wakes up after application of input power it begins bytesting the input impedance of the AC source to determine if itconnected to the AC grid (low impedance) or to a ballast (highimpedance). If input power is determined to be provided by a ballast theconfiguration is set for a typical ballast. Further testing of theballast impedance is then done to determine which ballast type ispresent. The ballast type is then used to set the specific transferfunction for optimal power factor and distortion at the ballast input

Electronic Accessory

In one embodiment of the LED system, there is an Electronic Accessorylocated in the front center portion of the LED system, an optimumlocation for the Electronic Accessory as:

a. This is at airflow inlet thereby experiencing the coolest air.

b. The front surface generally has unobstructed view of the area ofinterest which is useful if the electronic accessory is, for example, avisible or infrared camera. The front also allows unobstructed emittingand receiving of wireless signals, for example, radio frequency such asWiFi, Bluetooth, Z-Wave, Thread, Zibgee or other wireless signals. Thefront surface is also particularly advantageous for unobstructed opticalcommunication signals such as LiFi to and from the lighting system.

c. The center location allows for an optical accessory with a centeropening to be easily placed over the electronic accessory and rotatearound the accessory without interference.

In some embodiments, the electronic accessory has electrical connectionsto draw power from the main lighting unit including 12V, 5V or 3.3V.Another set of electrical connections may send a dimming signal, forexample 0-10V, PWM back to dim the main LED system. There may also bedata communication lines using protocols such as SPL, I2C, SPI in orderfor the electronic accessory to communicate with the main lamp assembly.The electronic accessory further has wireless communication capabilitiesto receive data to dim the light. The wireless unit may also emit datasignals to communicate with other lighting system as well to a controlunit.

In other embodiments, the electronics accessory may also contain onemore sensors such as day light sensors, occupancy, temperature, GPSlocation, world clock, altitude, humidity, vibration, acceleration.

A further embodiment of the GPS may include high sensitivity orultra-sensitivity that allows for an accurate location within buildings.A GPS sensor may be highly advantageous in combination with wirelesscommunication as it allows the LED system to report back its position.This may be highly advantageous for occasions such as in initial setupor commissioning of the systems where the location of the lamps isneeded, for example, identifying certain lamps controlled within whichzones. This may be also paired with other remote sensors in addition toan optional GPS sensor to more easily determine for which sensorscontrol which lights and within which zones. Without GPS, the locationof every sensor and led system must be manually recorded during theinitial installation and marked onto some floor plan. With the proposedGPS sensor, both the lighting locations and or other optional sensorscan be automatically generated.

In some embodiments, the electronics accessory may contain one or moredisplay lights. Such display lights may communicate some information,such as, for example, need for maintenance, replacement, faultcondition, availability of a parking spot, location of an item in awarehouse etc.

In various embodiments, the electronics accessory may contain one ormore audio elements, such as, for example, speakers, microphones, orbuzzers. Such audio elements may be useful, for example, in a publicannouncement (PA) system.

In some embodiments, the electronic accessory may be stackable so thatadditional electronic functions may be added. In such a stackedarrangement, it may be advantageous that the electrical interconnectionsare arranged so they also be easily stacked like a LEGO block.

Although various embodiments have been described with reference to theFigures, other embodiments are possible. For example, in the embodimentof FIGS. 8A-8F, the heatsink base 802 may thermally connect to the pins803 to define a thermally conductive path extending proximally along aheat transfer axis that defines an axial fluid communication path (e.g.,airflow paths 831) to conduct heat generated by the LED sourcesubstantially proximally to exhaust to ambient atmosphere. In theembodiment of FIGS. 9A-9B, the elongated sheet metal fins 901 thermallyattach to the heatsink base 902 to define a thermally conductive pathextending proximally along a heat transfer axis defining an axial fluidcommunication path (e.g., vertical air flow from the front 906 of LEDsystem to the interior 907 of the elongated fins and exiting above theelongated fins 910) to conduct heat generated by the LED sourcesubstantially proximally to exhaust to ambient atmosphere.

In the embodiment of FIGS. 10A-10F, spacing between the fins 1001, 1006at an outer perimeter 1004 is larger than the spacing of fins 1001, 1006near the center region 1008 to define a thermally conductive pathextending proximally along a heat transfer axis that defines an axialfluid communication path to conduct heat generated by the LED sourcesubstantially proximally to exhaust to ambient atmosphere. In theembodiment of FIGS. 10C-10D, the first fin 1001 has a first radiallength and a second fin 1010 has a shorter radial length. The fins 1001,1010 are arranged to define a thermally conductive path extendingproximally along a heat transfer axis defining an axial fluidcommunication path to conduct heat generated by the LED sourcesubstantially proximally to exhaust to ambient atmosphere.

In FIGS. 11A-11E, the fins 1101, 1102 thermally connect thermally andmechanically to either the central column 1103 and/or to the base 1104such that one or more thermally conductive paths extend proximally alonga heat transfer axis that defines an axial fluid communication path toconduct heat generated by the LED source substantially proximally toexhaust to ambient atmosphere.

In some embodiments, the construction of a heatsink, such as theheatsink of FIGS. 8A-11E, may require less metal thereby reducing theweight of a LED system. The heatsink may, advantageously, have moreairflow passageways when compared to a conventional LED system tominimize impedance. In various embodiments, the heatsink may increasethe operating life of a LED system because of the heatsink may lower theoperating temperature of the LED system. In some embodiments, the LEDsystem may be optimized for vertical orientation by providing asubstantially straight path for air to flow.

In various embodiments, with reference to FIG. 2C, the outer perimeter216 may define a first polygon and the inner perimeter 226 may define asecond polygon such the first polygon encompasses the second polygon. Insome embodiments, the outer perimeter 216 may share a portion of theouter perimeter 216 with a portion of the inner perimeter 226 such thatthe first polygon shares a boundary with the second polygon, forexample, as depicted in FIGS. 8D and 9A.

In some embodiments, a first plurality of LEDs may be projected unto afirst plane while a second plurality of LEDs may be projected unto asecond plane. In various embodiments, the first plane and the secondplane may be the same plane. In various embodiments, the first plane andthe second plane may be substantially parallel to each other and may notintersect each other such that when viewed from a top perspective, theLEDs defining the first plane encompass the LEDs defining the secondplane.

In various embodiments, an LED-based lighting system with enhancedconvective through-flow in an approximately vertical orientation mayinclude a light generation module comprising a plurality of LED sourcesarranged to illuminate along an optical axis in a distal direction. Theplurality of LED sources may be spaced apart from each other by one ormore open regions. For each one of the plurality of the LED sources ofthe light generation module may include a heat transfer member insubstantial thermal communication with the LED source such that the heattransfer member has a thermally conductive path extending proximallyalong a heat transfer axis that is substantially parallel to the opticalaxis. When in operation, the heat transfer member conducts heatgenerated by the LED source substantially proximally. The LED-basedlighting may further include an optic module having a plurality ofoptics spaced apart from each other by one or more optic open regionssuch that each optic corresponds to at least one of the LED sources.Each optic open region may correspond to one of the open regions whenthe optic module is aligned with the light generation module. The openregions defining at least one or more apertures such that the at leastone or more optic apertures defined in the one or more optic openregions aligns with a corresponding one or more apertures in the openregion to define an axial fluid communication path through the one ormore apertures and the one or more optic apertures, the axial fluidcommunication path parallel to the optical axis to remove heat from oneor more of the heat transfer members, wherein each of the axialcommunication paths extends proximally to the exhaust to ambientatmosphere.

A number of implementations have been described. Nevertheless, it willbe understood that various modification may be made. For example,advantageous results may be achieved if the steps of the disclosedtechniques were performed in a different sequence, or if components ofthe disclosed systems were combined in a different manner, or if thecomponents were supplemented with other components. Accordingly, otherimplementations are contemplated.

What is claimed is:
 1. A light distribution modification accessory foran LED-based lighting apparatus, the accessory comprising: an opticalbase comprising at least one optical path adapted to redirect at least aportion of light emitted by one or more elements forming an edge lightsource of a light module, wherein each one of the elements of the edgelight source comprises an outermost LED disposed proximate an edge of amechanical envelope comprising the light module, and wherein theelements of the edge light source are a subset of light module lightsource elements that are disposed at a greatest radial distance alongany radial direction from an optical axis of the light module; and, oneor more attachment members adapted to axially secure the optical base tothe light module in a plane orthogonal to the optical axis and in apredetermined axial position along the optical axis such that the atleast one optical paths are each in a predetermined opticalcommunication relationship with the edge light source, wherein when theoptical base is axially secured to the light module, the optical basealters an optical distribution of the edge light source such that theedge light source optical distribution changes from an unmodifiedoptical distribution to a modified optical distribution.
 2. Theaccessory of claim 1, wherein the light source disposed substantiallyproximate the edge of the mechanical envelope is disposed within about25 mm of the edge of the mechanical envelope.
 3. The accessory of claim1, wherein the modified optical distribution is substantially wider thanthe unmodified optical distribution.
 4. The accessory of claim 1,wherein the modified optical distribution has a substantially differentasymmetry than the unmodified optical distribution.
 5. The accessory ofclaim 4, wherein rotation about the optical axis of the optical basewith respect to the light module imparts a corresponding rotation aboutthe optical axis of the asymmetry of the modified optical distribution.6. The accessory of claim 1, wherein the modified optical distributioncomprises substantially more uplight than the unmodified opticaldistribution.
 7. The accessory of claim 6, wherein the substantiallymore uplight comprises between about 5% and about 40% of a total lightoutput of the light module.
 8. The accessory of claim 1, wherein themodified optical distribution has a substantially different diffusionthan the unmodified optical distribution.
 9. The accessory of claim 1,wherein the optical path comprises an input surface, a first reflectorsurface, and an exit surface.
 10. The accessory of claim 9, wherein theoptical path further comprises a second reflector surface.
 11. Theaccessory of claim 1, wherein the light module further comprises a heatsink in thermal communication with the edge light source and an opticalsystem in optical communication with the edge light source when theoptical base is not secured to the light module.
 12. The accessory ofclaim 1, wherein, when the optical base is axially secured in thepredetermined optical communication with the edge light source, theoptical base at least partially overlaps each of the elements of theedge light source.
 13. The accessory of claim 1, wherein, when theoptical base is axially secured in the predetermined opticalcommunication with the edge light source, the optical base onlypartially overlaps each of the elements of the edge light source. 14.The accessory of claim 1, wherein, when the optical base is axiallysecured in the predetermined optical communication with the edge lightsource, the light module emits a portion of light from the edge lightsource that has an optical distribution that is unmodified by theoptical base.
 15. The accessory of claim 1, further comprising a secondoptical ring concentrically disposed and substantially coplanar with theoptical base, and supported by at least one support beams extendingbetween the second optical ring and the optical base, and wherein thesecond optical ring comprises a second at least one optical path adaptedto redirect at least a portion of light emitted by one or more elementsforming a second light source.
 16. The accessory of claim 1, wherein theattachment comprises a releasable attachment operable to axiallydecouple the optical base from the light module.
 17. The accessory ofclaim 1, wherein the optical base is configured to rotate relative tothe light module while the optical base is coupled by the attachmentmembers to the light module.
 18. The accessory of claim 1, wherein theoptical base is formed with at least one interior aperture such that aircan flow parallel to the optical axis and through the at least oneinterior aperture.
 19. The accessory of claim 1, further comprising asubstantially flat optically transparent window extending across theinterior aperture.